RU2652777C1 - Estimation method of the quality of well cementing in low-temperature rocks - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention relates to the gas and oil industry and can be used in the development of northern hydrocarbon reservoirs, in particular when controlling the thermal insulating capacity of a thermal insulated column (TIC) and assessing the quality of wells cementing drilled in areas of low-temperature rocks (LP). Quality of the well cementing in the LP, equipped with TIC, is determined by isolating the different sections h_i, where i = [1…n] is the number of the site to be examined, taking into account the stability of the rocks, and / or their cavern porosity, and / or absorbing capacity. Before the injection of cement at the wellhead, temperature surveys are carried out, including the measurement of the temperatures of the selected equal volumes of samples of the displacement fluid, water and their mixtures. Taking into account the estimation of the specific heat release limit of the cement used at the well in a casing string annulus and the specific limit total heat quantity, which releases 1 kg of a cementing slurry when filling the entire annular space during cementation during hydration in the cement sheath, determine the index of the cementing quality factor K_qf.

EFFECT: expansion of functionality, consisting in using a heat-insulated casing column at an optimum depth; increase in the quality of fastening and sealing ability of the cemented wellbore, as well as the thermal insulating capacity of the direction used at the well.

1 cl, 1 dwg

Description

The invention relates to the gas and oil industries and can be used in the development of northern hydrocarbon deposits, in particular when monitoring the heat-insulating ability of a heat-insulated casing string (CTC) and evaluating the quality of cementing of wells drilled in areas of low-temperature rock (NP).

A known method of monitoring the technical condition of production wells, cementing wells using standard geophysical methods (Technique for monitoring the technical condition of production wells, Polozkov A.V., Potapov A.G., Korotaev Yu.P. et al., VNIIGAZ LLC, M ., 2000). The known method determines the basic provisions for monitoring the technical condition of production gas wells in the fields, indicating the overall complex and the specific work required to be performed. The method determines the geocryological conditions for the fields, considers the compliance of the selected well designs with complex geological conditions, the requirements for the quality of cementing, fastening, methods for monitoring the current state of the cement stone, the tightness of gas wells with the identification of the causes of annular pressures, leaks, and failures of underground equipment. However, this method is not applicable when using a thermally insulated casing string, as well as in casing strings with a diameter of more than 426 mm.

Closest to the proposed one is a method for assessing the quality of fastening of wells in the intervals of permafrost and low-temperature rocks (RF patent No. 2085727, class ЕВВ 47/00, publ. 07.27.1997), including measuring the temperature in the well during cement hardening. The method involves controlling heat generation during its hydration in a cement ring at known temperatures of permafrost (MMP) and NP surrounding the well, drilling fluid temperatures when drilling a well for launching a drilling fluid, discharging fluid inside a cemented string, temperatures of the string before running and when lowering it into the well, outgoing drilling and grouting solutions at the wellhead during casing cementing. Using the listed parameters in the studied interval, the specific heat release of the cement slurry in the annulus of the well is determined at the time of the study during cement hardening. In the studied interval, the heat released by the cement ring and redistributed between it and the rocks surrounding the well, the squeezing fluid and the casing for the time elapsed after the cementing is completed, until the cement hardens when it is hydrated, is also determined. The method also allows you to determine the maximum total amount of heat of hydration, which emits 1 kg of cement slurry when filling the annular behind the current space at different points in the study during the controlled process of cement hardening. The disadvantage of this method is the lack of necessary control and temperature measurements both directly inside the insulated column and in the cement ring, taking into account heat transfer in the well, typical when using current.

The objective of the invention is to develop a method for assessing the quality of cementing wells in low-temperature rocks, allowing the use of insulated casing.

The technical result of the invention is the expansion of functionality, which consists in using a thermally insulated casing at an optimal depth. An additional technical result of the invention is to improve the quality of the fastening and sealing ability of the cemented wellbore, as well as the heat-insulating ability of the direction used in the well.

The invention consists in the following. A method for assessing the quality of cementing a well in low-temperature rocks equipped with a heat-insulated casing and a thermo-measuring device is that, after drilling it, sections h _i are distinguished by conditions, where i = [1 ... n] is the number of the studied section, taking into account stability rocks, their cavernousness, absorbing abilities, thermal conditions. Before the cement is injected at the wellhead, thermometric studies are carried out, including measuring the temperatures of the selected equal volumes of samples of the squeezing liquid and water, which are placed in a thermos and mixed, after which the steady-state temperature of the mixture of squeezing liquid and water is recorded, the volumetric heat capacity of the squeezing liquid is determined as:

where - _W - the volumetric heat capacity of the displacement fluid, the sample taken at the wellhead during injection into the well (kJ / m ³ ° C),

- C _in - volumetric heat capacity of water, (kJ / m ³ ° C);

- t _W - temperature displacement fluid at the wellhead, (° C);

- t _in - water temperature at the wellhead, (° C);

- t _cm is the temperature of the mixture of squeezing liquid and water, (° C).

According to the data of thermometric studies in the course of cementing, the amount of total heat Q _xi redistributed between the cement ring and the volume of displacement fluid inside the column within this section is determined for each selected section h _i of the wellbore:

where: - t _ni - temperature of the displacement fluid inside the TOK within the boundaries of the i-th selected area at the beginning of the cement setting period during the cementing of the TOK, (° C);

- _ti is the temperature of the displacement fluid inside the TOK within the boundaries of the i-th selected area after the end of cement injection and during the hydration of cement during cementing of the TOK, (° C);

- r _VK - the inner radius of the pipe cemented TOK, (m).

Then determine the amount of heat Q _ki required to heat the inner surface of the cemented SLC, at an arbitrary point in time of the study after pumping cement into the well of the selected i-th section:

Where:

- With _ki is the heat capacity of the inner column, (J / m ³ ° C);

- τ _to - the outer radius of the pipe cemented TOK, (m).

Then determine the amount of heat Q _qi required to heat the selected i-th section of the cement ring cemented current:

Where:

- С _Цi - heat capacity of the selected i-th section of the cement ring, (J / m ³ ° C);

- t _нцi - temperature on the inner surface of the cement ring at the beginning of the cement setting period, (° C);

- t _ci - temperature on the outer surface of the selected i-th section of the cement ring at the beginning of the cement setting period, (° C);

- r _qi is the outer radius of the selected i-th section of the cement ring, (m);

- r _c1i is the inner radius of the selected i-th section of the cement ring, (m).

The total specific heat release q _{τцi is determined} during cement hydration in the annulus of the well 1 kg of cement slurry at the time of the study of the selected i-th area during cementing:

Where:

- Q _νцi - the total amount of heat released during hydration of the cement ring of the investigated meter interval of the i-th section;

- ρ _C - the density of the cement slurry in the annulus of the well, (kg / m ³ );

- τ _C - the time of the study during hydration of cement.

Taking into account the assessment of the total specific heat release q _τci during cement hydration in the annulus, an indicator of cementing quality coefficient K _kci TOK at a depth h _{i of the} selected i-th section is determined;

Where:

- q _p - the maximum total amount of specific heat that releases 1 kg of cement slurry when filling the entire annulus during cementation during hydration in a cement ring, (J / kg);

- on the basis of the obtained values of the cementing quality factor K _kci for all the studied i-th sections of the casing string, the quality of cementing of the _{current production complex} as a whole is judged:

In addition, the thermal insulation thermal resistance is additionally determined:

where U _tn is the thermal resistance of thermal insulation over the studied intervals i of cementing quality control during the lowering of the current, (m⋅h ° C / kJ); Where

- _{Δτ cj} - is the time of the current study at the j-th moment of time, (where j = 1, 2, 3 _,, m);

- by the indicator of thermal resistance, they judge the quality of the fastening of the investigated lowering interval of the current, and the cementing quality in the studied lowering interval is considered good at thermal resistance values U _t different from the regulated value U _{t of} manufactured and tested heat-insulated pipes from 5 to 10%, taking into account the error estimate .

According to the proposed method, when using a TOK with a thermometric measuring device (TIU), in the well after drilling under the heat-insulated direction, intervals of dense rocks and intervals of development of caverns and absorbing horizons are distinguished. Before the injection of cement at the wellhead, equal volumes of sampling fluid and water are sampled. At the time of sampling, their temperatures are measured, then these samples are placed in a thermos, mixed, and the steady-state temperature of the mixture of squeezing liquid and water is recorded. According to the data obtained, the volumetric heat capacity of the squeezing liquid is determined from the following expression (1).

Thermometry in the well is carried out both during flushing and downtime before cementing, and during cementing during the injection of cement and squeezing fluid into the well, as well as in the process of the final hardening of cement in the annular space. For each selected interval i (i = 1,2, ..., n,) of the wellbore (as an example, n = 7, see the drawing), the amount of total heat Q _Жi redistributed between the cement ring of the TDC and the volume of displacement fluid located inside the column within one meter in the studied interval according to the formula (2).

Next, determine the amount of heat Q _ki , which went to heat the inner surface of the cemented current at the jth time of the study (where j = 1, 2, 3 _,, m) within one meter in each studied i-th interval after cement injection in well using expression (3).

The amount of heat Q _qi that went into heating the i-th section of the cement ring of the cemented current is determined using expression (4).

Taking into account the assessment of the total amount of specific heat release of the grouting material used in the well, determined by the formula (5), under the appropriate temperature conditions in the annulus q _p , the cementing quality indicator K _kci TOK at a depth h _i in the studied interval is determined (where i = [1 ... n]) is the number of the studied area from the expression using expression (6).

According to the obtained values of the cementing quality index K _kci , calculated for all casing intervals i, the quality of cementing of the _CTC is judged. The quality of cementing of the CTC is judged by the obtained values of the thermal resistance index U _tn (defined by formula (7). If the thermal resistance index does not differ from the regulated value of the thermal resistance of manufactured and tested thermally insulated pipes, taking into account the estimation of the error in determining U _tn , more than 5-10% (i.e., not less than U _tn , the regulated value of the manufactured thermally insulated pipes used in the lining), then the quality of cementing in the studied intervals taking into account the heat The supporting ability of the lining is considered satisfactory.

The average value of К _кц for all studied intervals in a thermally insulated column should not be less than the corresponding value regulated for wells in the IMF and NP zones in the studied interval Н = Σh _i for i = 1, 2, 3 n. The determination of the quality of cementation of the CEC in the low temperature interval is carried out on the basis of quantitative estimates of the limits of variation of the indicator of the coefficient of quality of cementing K _kci :

According to the indicator of cementing quality factor К _кцi determine:

- zone with the absorption of drilling and cement slurries at К _кцi≥ 1.1;

- an area with good K _sci columns at 1.1> K _sci ≥0.7;

- a zone with satisfactory K _sci columns at 0.7> K _sci ≥0.4;

- an area with poor quality K _kci columns at 0.4> K _kci≥ 0.1;

- a zone with no cement behind the column or its setting at 0.1> K _ktsi ≥0.

The invention is illustrated by the drawing, which shows the upper section of the well lowered into the drilled well.

In the lower section, the trunk has a smaller diameter into which the casing is lowered without thermal insulation.

The upper section of the well includes - an inner pipe - 1, which has an elongated direction; outer pipe sheath - 2; thermal insulation - 3; a heat-insulated section - 4, having, for example, an elongated direction and a non-heat-insulated section - 5; TIU - 6 with a thermometric cable. The inner pipe 1 is filled with squeezing liquid - 7; behind the outer pipe-shell there is a cement ring - 8; well bore under the heat-insulated section - 9; the borehole under the non-insulated section and its cement ring - 10. Caverns - 11 are filled with drilling fluid. The drawing shows the interface between the thicknesses of the IMF and the underlying NP - 12, as well as the joints of double-walled heat-insulated pipes - 13. Positions 14-16 in the drawing reflect the calculated dependences of the temperature distribution on the radius at the base of the IMF, at the initial time τ _τ1 = 0 h (after the end of the injection of cement into the annulus), and at subsequent times during the setting (hydration) τ _c2 = 20 h, and at the time of the final hardening of the cement τ _c3 = 36 h), respectively. In addition, in the drawing, in the thickness of the IMF - h _m, different sections of h _i , (h ₁ ... h ₅ ) are highlighted in the field of cementing and heat-insulating ability, and in the zone of the NP - different sections of h ₆ and h ₇ .

The length h _{i of the} investigated sections of the _{current transformer} in depth is determined by the stability of the values of _ti , t _ni , t _ts1i , t _nci on them. With a significant change in the values of the given temperatures in the study of the current in different depth h _i sections, intervals are allocated to separate zones in which thermal studies are carried out, namely, taking into account specific conditions (in zones with different lengths h _i with different borehole cavernosity with different thermal conditions , the initial temperatures of the rocks and various temperatures of their heating during research), for example, in zones allocated along the body of casing pipes (TOT) and in the areas of pipe joints in the TOK.

The invention uses the technology of drilling the barrel to the design depth, including initially to the depth of the descent of the two-section direction with a large-sized bit, followed by drilling a non-heat-insulated section under the run using a bit of a smaller diameter. In this case, technology can be used that provides the smallest thawing of the permafrost and, accordingly, the cavernous trunk, both in frozen rocks and in lower located NPs, where there is no ice.

The invention can be applied to the upper section of the well, equipped with a current transformer with TIU (6) located behind the outer pipe (2), as well as with the descent of the TIU cable and behind the lower section with a temperature recording device installed on the wellhead.

In accordance with the invention, thermometry is also carried out in the wellhead zone with temperature measurements:

- drilling fluid at the inlet-outlet before lowering the current;

- flushing fluid during flushing after lowering the current flow before cementing;

- at the mouth of the cement mortar and squeezing fluid during cementing;

and also: - in the cement ring during setting-hydration of cement using TIU.

- during temperature control and inside the cemented column when lowering the thermometric cables into the squeezing solution inside the cemented column direction.

According to measurements conducted by the temperature t of the outer wall _u1 CPE in the cement annulus and t _w squeezing fluid within the TSC control wells thermal interaction with the surrounding rocks at WOC during the time τ _n the study upon setting cement hydration.

At the same time, the studied intervals h _i with different temperatures t _ntsi , t _ts1i , t _tsi in the cement ring, as well as with different bore diameters according to cavernometry data, are identified in the depth zone of the TOK in depth. For example, sections with different trunk diameters with caverns in the intervals h ₂ and h ₄ and without caverns, h ₁ , h ₃ , h ₅ , h ₆ and h ₇ , are identified by the cavernogram.

The drawing also shows the temperature distribution in the squeezing fluid t _lj , t _l (in the studied interval h ₅ at the bottom of the IMF according to the calculation example at the initial instant of time τ _c1 = 0 h, (after the end of the injection of cement into the annulus) and at subsequent times τ _c2 = 20 h and τ _c3 = 36 h when it is set.

Using TIU (for example, in the form of a fiber optic cable), temperature t _{t1 is monitored} in the cement ring (on its inner radius r _t1 = 0.20 m) continuously or at certain times from t _tsoi to t _ts3i in the studied intervals i, in an example for the interval h ₅ , as well as in the squeezing solution located inside the cemented column.

In squeezing the liquid inside CURRENT temperature measurements t _nJ, t _f is fixed, e.g., on the results of measurement of temperature deep geophysical thermometric device highly sensitive thermometry (HFT) t _nJ - a τ _tsi initial time = 0 h and t _w - in the final moments τ time _tsi = 20 h and 36 h using temperatures approximating the continuous recording or t _w in the intermediate time points (when a continuous recording is not carried temperature) in view of the nature of changes in the radius r = 0.20 m _u1 temperature t _u1.

Moreover, the initial temperature t _{nzh of the} squeezing fluid at the time τ _c = 0 after the end of its injection into the well can be estimated from the measured temperature of the squeezing fluid at the wellhead.

According to the invention, the specific heat emission of cement q _qi is determined during its hydration in the interval where the current is located by the analytical calculation method, and in non-heat-insulated areas (lower section of the elongated direction, see the drawing) - by the thermometric method, as well as using standard gas-dynamic research methods (GIS).

Using the TIU for example thermometric cable for TSC, temperature control is performed t _w, t _u1 WOC during the implementation of the technical state of insulation monitoring CURRENT, the definition of its thermal resistance U _t.

After the end of cement injection, the UT is determined by U _t from the measured temperatures of the displacement fluid inside the column and using TIU located on the outer wall of the TOK in the cement ring. The thermal resistance of the CTC is determined by the temperatures t _nj , t _W , t _nc , t _c1 , controlled after the completion of the injection of cement into the well, during the setting time τ _{cj of} cement (at specific time intervals _{Δτ cj} in the studied i-th interval of the location of insulated pipes in well), as well as when monitoring changes in the i-th temperature range inside the column, namely, in the squeezing fluid at the initial time and at the final time, while monitoring the temperatures on the inner and outer surfaces of the cement th _current ring, t _ntsi and t _ts1i .

The heat from the squeezing fluid into the cement ring through the CCP can be transferred both from the squeezing fluid and in the opposite direction, depending on the heating and heat exchange in the wellhead at the OZZ. The direction of the heat flux in the borehole with an OZZ in the studied interval can change the direction of the value when determining U _tn , therefore the temperature difference between the cement ring and the squeezing liquid can be taken as the absolute value: (t _нжi -t _ж1i ) - (t _нцi -t _ц1i ) _j , where j is the point in time of the study, and the sign of this value shows in which direction heat flows from the cement ring to the squeezing fluid inside the column or in the opposite direction during the hydration of the cement. This is taken into account in formula (7) when determining U _tn .

The index j indicated in formula (7) means that the noted temperatures can be determined at any time during the study, including in different intervals i along the current length.

It is more convenient to conduct studies at the initial time τ _cj after the end of the injection of cement, squeezing fluid and at the end of the OZC, while monitoring the temperature inside the cemented column and the quality of cementing of its insulated and non-insulated parts.

First, we consider an example of processing the results of thermometry in the proposed way when determining the thermal resistance U _t when cementing current.

After the end of the cement injection into the well (annular space), thermometry is carried out, for example, at the initial moment (0 hour).

After cementing the heat-insulated casing string, when idle, after τ _cj = 20.0 hours, the temperature is measured with a geophysical depth thermometer inside the cemented TOK. At the studied depth (research interval i), the temperature t and _i amounted to 10.2 ° C and the internal steel pipe of the TOK had the same temperature.

According to the temperature measurements of TIU on the outer wall of the TOK for 20.0 hours (at the time point τ _cj = 20.0 h), the temperature in the cement ring at a radius r _c1 = 0.20 m changed from t _nci = 5.5 ° C to t _c1i = -15.1 ° C.

To determine the thermal resistance of the current, it is necessary to know the volumetric heat capacity of the squeezing liquid C _g . Selection method of squeezing the liquid samples for the mouth and the known water volume heat capacity _C = 4184 kJ / m ³ ° C and the water temperature measured _at t = 17.0 ° C, and the temperature t _w = 12.0 ° C selected Sample mud and the measured temperature of their mixture t _cm = 14.7 ° C, placed in a thermos, determine the heat capacity C _{w of the} squeezing liquid, which is pumped during cementing inside the current:

where t _W is the temperature (0.5 L) of the squeezing liquid;

t _in - temperature (0.5 L) of water (° C);

t _cm - temperature of the mixture (volume 1.0 l) of the squeezing liquid and water (° C);

C _in - heat capacity of water (kJ / m ³ ° C);

C _x - specific heat squeezing fluid sample taken at the wellhead for injection into the wellbore (kJ / ^m3 ° C).

When conducting tests to evaluate the thermal resistance U _{tn the} current in the considered example, the initial temperature of the squeezing fluid, t _ni , in the studied interval during idle time of the well at the borehole over a period of time t _cj from 0 to 20.0 h increased from 10.2 ° C to t _W = 11.1 ° C. At the same time, for 20.0 hours inside the column in the i-th interval, the heating fluid and steel pipe (CCP) were heated, which consumed, respectively, the heat Q _qi and Q _ki :

The thermal resistance U _{mn of the current is} determined taking into account the heating time (the first time interval of the study j is 20 hours), during cement hydration (time of _{wet cleaning} ) according to thermometry data at temperature control t _Цi , t _жi,:

The values “+” or “-” obtained from expression (7) before U _t indicate that heat is transferred from the cement ring to the squeezing fluid through the CCP or vice versa from the squeezing fluid to the cement ring.

When conducting a study of thermally insulated pipes on a field stand before their descent into the well, their thermal resistance U _tn = 0.61 h⋅ ° C / kJ. The discrepancy in the determination of the heat-insulating ability of the TOK pipes, namely, their thermal resistance obtained at the bench and in the well, is insignificant, which confirms their good technical condition after lowering into the well and cementing. In addition, in the study of the proposed method, there is a high accuracy in determining U _tn in the well during its cementing: the discrepancy in the determination of U _tn was 0.034⋅h⋅ ° C / kJ.

An example of assessing the quality of cementing and fastening a thermally insulated casing of the proposed method.

When evaluating the quality of casing string cementing, the temperatures of the flushing, grouting mortars and squeezing fluid injected into the well are measured in preparation for fastening and when the well is secured with a heat-insulated casing in MMP and NP, as well as the solutions that go to the mouth behind the cemented cement slurry before the cement grout is pushed.

After washing the wellbore downhill, the standard logging is carried out to determine the lithology of the section, ice content, water cut and the presence of gas hydrate rocks (for example, according to the MOSK method described in the Method for Monitoring the Technical Condition of Production Wells, OAO Gazprom, VNIIGAZ LLC, M ., 2000). Then, cavernometry of the trunk is carried out with the identification of caverns, with the determination of the volume and configuration of the trunk in depth in the interval of occurrence of the permafrost in the NP.

The data obtained during geophysical studies of the section in the IMF and NP are used to assess the quality of fastening and cementing when using CT, including when evaluating the heat and mass transfer of a well with IMF and NP when attaching, as well as when using a combined CT, including heat-insulated pipes in the upper section at the presence in the upper part of subsiding icy IMF, and in the lower part of the non-heat-insulated section of conventional single-wall casing pipes. The proposed solutions for the identification of permafrost over the direction along the GIS with the identification of their ice content, allow us to determine the optimal depth of descent of the insulated section.

When lowering the TOK into the well, TIU, as well as a thermometric cable, are fixed on its outer pipe. TIU can also be lowered into a thermometric tube mounted on the outer wall of the TOK for temperature measurements in the annular space. The use, for example, sometimes of a steel tube fixed on the outer wall of the direction for lowering the TIU into it allows you to prevent cases of destruction of the TIU and its failure, which sometimes occur during descent and fixing, cementing the direction to the well.

Thermometry in the well is carried out, for example, using a TIU-thermometric cable installed behind the CCP, both during flushing and downtime before cementing, and during cementing when cement and drilling fluid are pumped into the well, as well as in the process of cement setting τ _c

The cementation quality assessment of the heat-insulated section of the TOK and its non-heat-insulated lower section is carried out using the cementation quality indicator by the formula (8).

With the thermometric control method, the cementing quality of non-heat-insulated columns and current is recognized as good when the cementing quality coefficient is 0.7≤K _ktsi <1.1; satisfactory at 0.7> K _ktsi ≥0.4, if K _ktsi ≥1.1, it is believed that the wash and cement slurry was absorbed during cementing. If K _kci <0.4, cementing quality is considered poor, in which the annular space may not be completely filled with cement.

For non-insulated sections of the TOK, cementing quality assessment can be carried out by the thermo-method described, for example, in RF patent No. 2085727.

The specific heat limit of cement, q _pi , used at the well as grouting material, is determined taking into account the thermal conditions in the studied intervals h _i and when comparing with values of q _p obtained by examining the samples in the laboratory at the bench under the appropriate thermal conditions.

Evaluation of the quality of cementing and fastening of the TOK in the OZZ process, according to the proposed method, is carried out by measuring the temperature in the well with the OZK using a thermal method, by assessing the heat-insulating ability of the cemented TOK with the determination of its thermal resistance and the quality of cementing in MMP and NP. Prior to cementing, into the annular cemented space of the TOK well with TIU, they control by measuring the temperature of the washing solution and the injected cement, then samples of the displacement fluid injected into the column are taken, and the temperature is monitored using wellhead thermometers during cementing.

- удельное тепловыделение цемента.After the injection of cement during idle time, for a point in time τ _c1 = 20 h, Q _νсij is determined - the amount of heat released by the cement during hydration, and

- specific heat of cement.

Quality cementing current (for the upper section of the elongated direction, e.g., with an outer radius r TOT _nt r = _u1 = 0.20 m and an inner radius equal to TOT-CURRENT r _cr = 0.112 m) was assessed by determining the specific heat q _q cement annulus space, which is determined based on the calculated bulk density Q _vi heat source in the cement sheath in the annulus is cemented investigated in i-th interval with the previously performed temperature measurements in the cement annulus and the TSC for squeezing liquid - VNU When the current in this range.

First, temperature is measured in the range of h ₅ (see the drawing), in the context of which frozen rocks with an initial temperature of “-1.0 ° C” and mass ice content M = 30 kg / m ³ with a trunk radius determined by a cavernogram equal to r _c = 0.34 m (corresponds to the outer radius of the cement ring in the studied interval), and the measured temperatures t _nci , t _c1i , t _nci , _tcii , _tcci , _tci at different points in time: _τci = 0 h; 20.0 h; 36.0 hours

- where t _нкi and t _кi temperature of _current in the initial and final moments of the period of cement setting, (° C).

Then we will evaluate the quality of cementing of the TOK in the marked interval h ₅ (see the drawing) at the time of the study τ _tsi = 20.0 hours

The temperature measurements determine the heat that went into heating the squeezing liquid and the current (its internal steel pipe, the heat insulation and the external current due to the small heat are not taken into account), the heat that was released during the setting of cement, during its hydration and heat redistribution in the cement ring, inside the TOK and in the surrounding rocks.

гидратации цемента и оценивают качество цементирования ТОК в исследуемых интервалах i=5 с учетом геокриологических и тепловых условий, влияющих на теплообмен скважины с окружающими породами в процессе гидратации, схватывания цемента.Given the redistribution of heat in different zones, specific heat is determined

hydration of cement and evaluate the quality of cementing of SOC in the studied intervals i = 5, taking into account geocryological and thermal conditions that affect the heat transfer of the well with surrounding rocks during hydration, cement setting.

The heat capacity of the thermal insulation of the thermal insulation layer and the outer shell of this thermal insulation in the study in the considered examples are not taken into account because of their smallness.

. Толщина исследуемого интервала i составляет h_i5=15 м, в котором отмечают характерные «стабильные тепловые условия». Так при замере температур в этом интервале на момент времени τ_ц1=0 ч замеренные температуры составляли t_нцi=5,5°C, t_нжi=6,2°C, t_нкi=6,2°C, а в момент времени исследования τ_ц2=20 ч они были равны t_нцi=15,1°C, t_нжi=7,1°C, t_нкi=7,1°C. Как видим за счет выделения тепла гидратации

эти температуры за время от τ_ц1=0 ч до τ_ц2=20 ч повысились.At a depth of h ₅ in the frozen interval during the study (see drawing, (curve 15) at a time point τ _c2 = 20 h, the specific heat released in the cement ring is determined

. The thickness of the studied interval i is h _i5 = 15 m, in which the characteristic “stable thermal conditions” are noted. So, when measuring temperatures in this interval at a time instant τ _c1 = 0 h, the measured temperatures were t _nci = 5.5 ° C, t _nci = 6.2 ° C, t _nci = 6.2 ° C, and at the time of study τ _c2 = 20 h, they were t _tsi = 15.1 ° C, t _nzhi = 7.1 ° C, t _nki = 7.1 ° C. As we see due to the heat of hydration

these temperatures increased from τ _c1 = 0 h to τ _c2 = 20 h.

лед протаивал при изменении температур в породах, прилегающих к цементному кольцу, от температуры t_ф1=-1,0°C до t_ф2=0°C и Δ_tф=0-(-1.0)=1,0°C (принимают абсолютное значение Δt_ф=1,0°C).When conducting research in the interval h _i5 , represented by frozen loamy rocks, lasting 20 hours, when determining

ice thawed when the temperature in the rocks adjacent to the cement ring changed from temperature t _f1 = -1.0 ° C to t _f2 = 0 ° C and Δ _tf = 0 - (- 1.0) = 1.0 ° C (take the absolute value Δt _f = 1.0 ° C).

The total heat capacity of the rocks, taking into account the properties of frozen rocks during heat exchange of the well with them, as well as the heat capacity of the mineral component of frozen rock (C _mn ), for example, equal to 2300 kJ / m ³ ⋅ ° C, and thawing of ice with an increase in rock temperature from -1, 0 to 0 ° C in the zone from r _c = 0.34 m to r _{vl of the} thermal effect of the well in the studied interval with the specific mass of ice M = 30 kg / m ³ and the heat of phase transition - I = 334 kJ / kg:

The observed heat capacity is taken into account when calculating the borehole heat during its mounting, cement setting time Δτ for _u1 = 20 hr with the surrounding rocks, wherein p r The radius of influence for the specified time _is determined from the formula:

where λ _M is the coefficient of thermal conductivity of frozen rocks (kcal / m⋅h⋅ ° C).

Given the obtained value of the radius of influence r _VL = 0.392 m determine the heat transfer coefficient α _i from the well, starting from the outer wall of the cement ring to the surrounding rocks:

Given a certain radius r _{vl of} thermal influence, at which the temperature in frozen rocks is _ttv = 0 ° C, the heat transfer coefficient α ₂ from the outer wall of the cement ring to the surrounding rocks at a radius r _c = 0.34 m is α ₂ = 26, 25 (kJ / m ² ⋅h⋅ ° C).

Taking into account the noted heat transfer to the surrounding rocks, the bulk density Q _{vцij of} heat sources in the cement ring is determined in the studied interval i = 2 at the time of the study during setting, hydration τ _Ц2 = 0 h:

where λ _qi is the coefficient of thermal conductivity of the cement ring (kcal / (m⋅h⋅ ° C).

за 20 ч с учетом рассчитанной средней величины Q_vi, характеризующей объемную плотность источников тепла в цементном кольце в исследуемом интервале h₂ при плотности цемента ρ_ц=1500 кг/м³ и с учетом теплообмена цементного кольца при схватывании цемента с продавочной жидкостью внутри цементируемой колонны и ее внутренней стальной колонны.Next, determine the value of the specific heat of cement

for 20 hours, taking into account the calculated average value of Q _vi , which characterizes the bulk density of heat sources in the cement ring in the studied interval h ₂ at a cement density ρ _c = 1500 kg / m ³ and taking into account the heat exchange of the cement ring when cement sets with squeezing liquid inside the cemented column and its inner steel column.

. Количество тепла, пошедшее на нагрев цементного кольца, продавочной жидкости и наружной колонны составит:Then, the redistribution of heat released during hydration in the studied interval is determined, and the amount of heat required to heat the cement ring Q _qi , and the squeezing liquid Q _qi inside the _{current transformer} , as well as the internal steel column Q _ki . Taking into account the obtained values of Q _Цi , Q _Жi , Q _Кi , the specific heat of cement is evaluated

. The amount of heat used to heat the cement ring, squeezing fluid and the outer column will be:

в течение 36 ч необходимо определить тепловыделение за период время τ_ц от 20 до 36 ч.To determine the total specific heat

within 36 hours it is necessary to determine the heat release for a period of time τ _C from 20 to 36 hours

для момента времени τ_ц3=36 ч при Δτ_ц=τ_ц3-τ_ц2=16 (ч).As an example, we define Q _vuij and

at time τ _w3 = 36 hours at Δτ = τ _i -τ _{w3 n2} = 16 (h).

According to the results of the measured temperatures at time instants τ _C2 = 20 h and τ _C3 = 36 h:

гидратации, выделяющееся в течение времени Δτ_ц2=16 ч с учетом измеренных температур в моменты времени τ_ц2=20 и τ_ц3=36 ч в течение 36 ч теплового воздействия проведения исследований.determine the bulk density Q _{vцij of} heat sources in the cement ring and the specific heat

hydration released during the time Δτ _c2 = 16 hours, taking into account the measured temperatures at time instants τ _c2 = 20 and τ _c3 = 36 hours for 36 hours of the thermal effect of the studies.

приводятся ниже:The calculation results of Q _vсij and

are given below:

Given the values of the measured temperatures at Δτ _c = 16 h is determined by:

Given tsem cient hydration during the study from 0 to 20 hours (Δτ _u1 = 20 h), the amount of specific heat q _ts1i hydration range studied was 50.40 kJ / kg, and during the continuation of research for the time Δτ _n2 = 16 h, respectively, q _q2i = 14.4 kJ / kg.

During 36–40 hours, usually not less than 70–80% of the heat of hydration is released, and during the time Δτ _q2 = 36 h, according to the considered example, the total q _qi was q _qi = q _q1i + q _q2i = 50.4 + 14.4 = 64.8 (kJ / kg).

Considering the results of testing cement samples on a bench that was used in wells (the maximum possible specific heat release of cement, q _p , is about 100 kJ / kg), the obtained indicator of cementing quality coefficient in the interval i = 1 is

К _кц1 = q _ц / q _п = 64.88 / 100 = 0.65 in the interval of length h ₅ = 15 m. At К _кц5 = 0.65 in the studied interval i = 2 and, taking into account that after 36 h, the heat and the setting of cement will continue and K _sc2 reaches a value of 0.7 and higher, the cementing quality in the interval h ₂ is considered good.

In the interval for lowering the current in the upper section according to the method, 5 intervals h _i q _qi (i = 1 ... 5) are _identified , according to which K _{c was} studied, and in the lower non-insulated section K _c , 2 intervals q qi were _determined (i = 6 ... 7 ), the results are presented below:

Thus, in the zone of descent of the TOK, the value of the total index K _kts of cementing quality of the TOK, determined (see 8), amounted to K _{ktsv of the} upper section:

The cementing quality of the upper thermally insulated section with a length of 72 m is rated as satisfactory.

According to the lower non-heat-insulated section of the direction (thermal resistance U _{nt of the} non-heat-insulated pipe - the lower section is not more than 0.005⋅h⋅ ° C / kJ taking into account a small layer of clay cement on the inner wall of the pipe, about 2 cm) using the thermometric method of cementing quality assessment (in the interval h ₇ = 18 m) amounted to K _ctsn = 0.54 and, accordingly, in general, the cementing quality of the direction is also assessed as satisfactory.

According to the results of the study, at the descent depth of the insulated section, in the considered example up to 90 m, the coefficient value of the upper section of the direction К _кц = 0.47 is satisfactory, and according to the state of the heat-insulating ability of the current transformer at U _t = 0.564⋅h⋅ ° C / kJ, as good . Considering that the thermal resistance of the casing pipes according to the results of their tests prior to descent was u _t = 0.61⋅h⋅ ° C / kJ, and the value of U _t obtained when testing the current flow in a well differs by no more than 7.5%, then and the quality of the fastening can be assessed in general as satisfactory.

The studies carried out by standard methods showed that the cementing quality of the lower section of the elongated direction is also assessed as satisfactory, and in general, the quality of fastening of the casing two-section interval with MMP and NP is estimated as satisfactory.

The use of this technical solution allows technical control of the heat-insulating ability (thermal resistance) of the cemented heat-insulated casing string and to evaluate the quality of its cementing by the thermometric method in IMF and NP, when other standard geophysical methods (for example, acoustic) do not work, for example, in the case of a large diameter casing string - 508 mm or more.

The invention allows for operational monitoring of the quality of thermal insulation of the TOK in wells immediately after it is lowered into the well during cementing. The proposed solution allows you to control the thermal interaction of the well with MMP and NP, both during the construction of the well, and in the process of its further operation when using TIU installed on the well.

при гидратации позволяет повысить точность определения

, а также оценить теплоизолирующую способность ТОК в процессе ее цементирования.Continuous monitoring of temperature t _c1 in the cement ring on the outer wall of the _{current transformer} (when installing a fiber optic thermometry cable on it) and, accordingly, its specific heat

during hydration improves the accuracy of determination

, as well as evaluate the heat-insulating ability of the current in the process of cementing it.

The invention also makes it possible to determine the thermal resistance of thermal insulation of the SOF in the area of joints, taking into account the fact that the thermal insulation (heat-insulating ability of the column) in the area of the joints of the SOF (at the joints of the SOF in the column) can significantly differ from the heat-insulating ability in the body of the SOF, including worse depending on the joint thermal insulation technology used at the well. When monitoring the thermal insulation of the TOK, defects in the thermal insulation of joints during fastening can be detected.

Knowing the thermal resistance of the TOK thermal insulation through the body of the TOT and in the places of their joints, it is possible to fully control the technical condition of the TOK by their heat-insulating ability (in terms of U _t ) in the well.

Claims (38)

1. A method for evaluating the quality of cementing a well in low-temperature rocks (NP), equipped with a heat-insulated casing (TOC) and a thermo-measuring device (TIU), which consists in the fact that in the well after its drilling, sections h _i are distinguished by conditions, where i = [ 1 ... n] - number of the studied area, taking into account the stability of the rocks, their cavernousness, absorbing abilities, thermal conditions; Before the cement is injected at the wellhead, thermometric studies are carried out, including measuring the temperatures of the selected equal volumes of samples of the squeezing liquid and water, which are placed in a thermos and mixed, after which the steady-state temperature of the mixture of squeezing liquid and water is recorded, the volumetric heat capacity of the squeezing liquid is determined as:

, where C _W is the volumetric heat capacity of the squeezing fluid taken at the wellhead when pumped into the well (kJ / m ³ ° C), C _in - volumetric heat capacity of water, (kJ / m ³ ° С); t _{W is the} temperature of the displacement fluid at the wellhead, (° C); t _in - water temperature at the wellhead, (° C); t _cm is the temperature of the mixture of squeezing liquid and water, (° C); according to the data of thermometric studies in the course of cementing the current for each selected section h _i of the wellbore, determine the amount of total heat Q _Жi redistributed between the cement ring of the current and the volume of displacement fluid located inside the column within the boundaries of this section:

where t _nzhi is the temperature of the displacement fluid inside the TOK within the boundaries of the i-th selected area at the beginning of the cement setting period during the cementing of the TOK, (° С); t i _{i is the} temperature of the displacement fluid inside the TOK within the boundaries of the i-th selected area after the completion of cement injection and during cement hydration during cementation of the TOK, (° С); r _VK - the inner radius of the pipe cemented TOK, (m); determine the amount of heat Q _ki required to heat the inner surface of the cemented SLC at an arbitrary point in time after the injection of cement into the well of the selected i-th section:

where C _ki is the heat capacity of the inner column, (J / m ³ ° C); r _to - the outer radius of the pipe cemented TOK, (m); determine the amount of heat Q _qi required to heat the selected i-th section of the cement ring cemented current:

where C _ti is the heat capacity of the selected i-th section of the cement ring, (J / m ³ ° C); С _{нцi -} temperature on the inner surface of the cement ring at the beginning of the cement setting period, (° С); t _{ci is the} temperature on the outer surface of the selected i-th section of the cement ring at the beginning of the cement setting period, (° С); r _qi is the outer radius of the selected i-th section of the cement ring, (m); r _c1i is the inner radius of the selected i-th section of the cement ring, (m); determine the total specific heat q _qi during the hydration of cement in the annulus of the well 1 kg of cement slurry at the time of the study of the selected i-th area during cementing:

where Q _νсi is the total heat released during the hydration of the cement ring of the studied meter interval of the i-th section; ρ _c - the density of the cement slurry in the annulus of the well, (kg / m ³ ); τ _C - the time of the study during hydration of cement; taking into account the assessment of the total specific heat release q _τci during cement hydration in the annulus, an indicator of cementing quality coefficient K _kci TOK at a depth h _{i of the} selected i-th section is determined;

, where q _p is the maximum total amount of specific heat that releases 1 kg of cement slurry when filling the entire annulus during cementation during hydration in a cement ring, (J / kg); according to the obtained values of the cementing quality factor K _ki for all the studied i-th sections of the casing string, the quality of cementing of the _{current production complex} as a whole is judged:

2. The method according to p. 1, characterized in that it further determines the thermal resistance of thermal insulation:

where U _tn is the thermal resistance of thermal insulation at the studied intervals i of cementing quality control during the lowering of the current, (m⋅h ° С / kJ); Where _{Δτ cj} is the time of the current study at the j-th point in time, where j = 1, 2, 3, ..., m); according to the thermal resistance indicator, the quality of the fastening of the investigated drainage interval is estimated, and the cementing quality in the studied drainage interval is considered good at thermal resistance values U _t different from the regulated value U _{t of} manufactured and tested heat-insulated pipes from 5 to 10%, taking into account the error estimate.

Images