RU2204700C1 - Method of oil production - Google Patents

Abstract

FIELD: oil producing industry, more specifically, group of oil production methods. SUBSTANCE: method consists in well drilling and subsequent drilling from said well of horizontal wells; preliminary determination of oil supply channel; well drilling to horizons underlying oil-bearing beds or surfaces of crystalline basement; drilling of horizontal wells over circumference from main well bottom hole, below bottom of oil-bearing bed; injection through horizontal wells of isolating substance; well deepening and its testing. EFFECT: increased oil production. 6 cl, 3 dwg

Description

 The invention relates to the field of the oil industry, and more specifically to a group of methods for oil production.

 Known are traditional methods of oil production from oil deposits, including drilling a well to depths, involving crossing oil horizons, lowering the casing string, cementing it and inflowing it, followed by oil production from productive formations (Sputnik oil and gas geologist: Handbook / Ed. I.P. Chalovsky. - M .: Nedra, 1989, 376 s). However, the process of cost-effective oil production from the reservoir, as a rule, takes a limited time and at a late stage requires measures to increase oil production.

 Modern technologies of oil production at a late stage of development are associated with the injection of large volumes of water in order to displace oil into a production well. Injected water, firstly, increases the reservoir pressure, and secondly, greatly complicates the production process and reduces its profitability (Shustef I.N. Geological foundations of technological solutions in the development of oil fields. -M .: Nedra, 1988, 199 s).

 There is also a known method of developing a productive deposit in a crystalline basement (US Pat. RF 2111347, application form 13.10.97; publ. 05.20.98, M. cl. E 21 B 43/20). By the method, a region with a large number of productive deposits located in a sedimentary cover is selected. The depth of the crystalline basement under the sedimentary rocks is determined in the earth's crust of the selected region. Determine in the crystalline basement the zones of compaction with zero permeability and the zone of decompression with permeable reservoirs located under the zone of compaction. In addition, the dimensions and configuration of the decompression zone are determined, and the shape, thickness and area of the seal zone are analyzed. If there is a domed shape and thickness and area of the compaction zone sufficient to hold upward fluid flows, at least one production well is drilled through the domed part of the compaction zone into the decompression zone. In the decompression zone, reservoirs and non-reservoirs are determined. The reservoir strata are tested for inflow starting from the lower reservoir stratum. In the presence of an influx of productive fluids, the well is put into operation. A further grid of production wells is determined depending on the reservoir properties of the reservoir. This allows you to increase the accuracy of determining the reserves of productive deposits in the crystalline basement and increase the efficiency of their development.

 However, this method relates to the search and development of deposits in the traps of complex structure, but, in fact, of the usual type and contains the disadvantages inherent in traditional oil production (the development of the reservoir itself, its flooding, the use of enhanced oil recovery methods, etc.).

 The closest in technical essence are methods of oil production using horizontal and multilateral wells with horizontal branches passing directly through the oil reservoir. In this case, the useful length of the wells in the reservoir and, consequently, the drainage zone (filtration surface) increases, as a result of which the well production rate significantly increases (Bulatov A.I., Avetisov A.G. Handbook of a drilling engineer. In 2 volumes Volume 1. - M .: Nedra, 1985, p.11).

 This method significantly increases the productivity of the well, however, as a rule, it is used for oil deposits occurring in the rocks of the sedimentary cover and is also focused on oil production from the reservoir.

 The present invention fundamentally changes the ideological approaches to oil production. It is proposed to carry out oil production directly from the oil supply channel connecting the oil reservoir to the deep reservoir. For this, it is necessary to establish the position of the oil supply channel, isolate it from the deposits and extract oil from it directly.

 Oil coming from the channel can be extracted for a long time (tens and hundreds of years), in this case, a stable flow rate is maintained. Waterflooding technologies are not required; oil is extracted almost anhydrous.

 In the proposed method, which consists in drilling a well and then drilling horizontal wells from its trunk, testing, the position of the oil supply channel is preliminarily determined, then the well is drilled to the horizons underlying the oil-bearing strata or to the surface of the crystalline foundation. Around the circumference from the bottom of the main well below the bottom of the oil-saturated formation, horizontal wells are drilled through which the insulating substance is pumped, then the well is deepened, after which it is tested. The position of the oil supply channel is determined by pre-conducted field studies of wells that produce oil from the productive horizons of the sedimentary cover, as well as pre-conducted geophysical studies.

 The essence of the proposed method is as follows.

 The development of some oil fields has been going on for over 100 years. During this period, the reserves of many of them have been fully developed, but oil production continues. An example of fields that have been under development for more than 100 years and are currently ongoing can be the fields of Azerbaijan, a number of oil fields in the North Caucasus, Ferghana, etc. These facts cannot be explained by the existing model of a one-time act of forming a field and extracting oil from the final reservoir of a modern traps.

 More and more facts are accumulating that may indicate a probable inflow of oil into the reservoir from deeper horizons. In some cases, in particular in the fields of Tatarstan, the Samara region and adjacent regions, oil inflow into the deposits of the terrigenous Devonian can occur only from the basement rocks lying directly below them.

 There is numerous and most diverse evidence of the close relationship of oil fields with discontinuous violations. But not all discontinuous violations, but only certain types of them, are associated with oil fields. These violations can be considered oil-bearing or oil-supplying. The oil content of the faults is usually not continuous, extending along their entire length, but is limited to narrow sections - oil supply channels, due to the activity of which the formation of oil fields occurs.

 Thus, each oil field was formed due to the inflow of oil fluid from deep sources through oil supply channels and consists of three main components: a trap filled with oil, a deep reservoir, which is the main supplier of hydrocarbon fluid and an oil supply channel connecting the deep reservoir to the reservoir. This channel can be active, retaining the connection between the field and the deep reservoir, or passive when this connection is broken, usually due to the oxidation of oil and turning it into a highly viscous fluid or solid bitumen. In undeveloped fields, an equilibrium state is established between the reservoir, the oil supply channel and the deep reservoir. In the process of extracting oil from the reservoir, the trap is partially freed up, as a result of which the balance between the deep reservoir and the reservoir is disturbed, and new portions of oil may flow through the channel if the oil supply channel has maintained an active connection with the deep reservoir.

 The oil that fills the trap over time becomes heavier and more viscous, while the oil that flows directly through the channel becomes lighter, less oxidized.

 The typical pattern of the dynamics of oil extraction from a field (deposit) is well known, when at the first stage its growth occurs, then the maximum level is indicated, then an inevitable decrease follows, and finally, at a very late stage, a relatively low level of production stabilization is established.

 Figure 1 shows a schematic diagram of oil production at the field, where 1 is the beginning of development; 2 - maximum level of production; 3 - stabilization of oil production at a late stage corresponds to the flow rate of oil flow through the oil supply channel - 4.

 In the period from 1 to 3 - oil is produced mainly from a trap; at a late stage (after point 3), production is predominantly due to oil inflow through the oil supply channel (4). At this stage, a balance is established at the fields between the volumes of oil produced and its inflow. It is at a late stage that the oil supply channels are activated and the level of oil production in this period can be considered as the flow rate of the oil supply channel of this field (deposit). Prior to this stage, oil is recovered almost exclusively from the trap.

 At the late stage of development, the level of production stabilization is established at many fields, ranging from 3-5 to 17-20% of the maximum production and lasts for a long time - many decades. With full co-optation of all oil supply channels in the field, production from them will correspond to this level.

 Oil supply channels are located within the area of deposits and can be traced both in the sedimentary cover and in the basement rocks. They probably represent fracture zones at the intersection of oil-supply faults.

 Prediction of the location of channels in the plan within the developed field is established on the basis of field data, and for undeveloped or projected fields - based on the results of geophysical studies. So, under large oil fields at depths of the order of 15–20 km, intense dynamic anomalies are observed at seismic time sections, from which narrow, slightly expanding upward subvertical anomalies stretch. The first of them can be considered as a probable deep reservoir, and subvertical zones - as possible oil supply channels.

 Oil entering the reservoir from deep sources at a late stage of development spreads over the reservoir. Modern production technologies are associated with the injection of large volumes of water in order to displace oil into the production well. Injected water, firstly, increases reservoir pressure, which negatively affects the flow rate of the oil supply channel, preventing the flow of new portions of fluid, and, secondly, greatly complicates the production process and reduces its profitability.

 In contrast to existing methods of oil production from deposits, it is proposed to extract it directly from the oil supply channels. To implement this proposal, the zone of the oil supply channel must be isolated from the reservoir (s) and oil extracted directly from the oil supply channel.

 The essence of the proposed method can be explained in figure 2, 3, which shows a diagram of the isolation and development of the oil supply channel (figure 2 - profile, figure 3 - plan). Figure 2 shows the well 5, intersecting sedimentary cover sediment 6 and oil reservoir 7, artificial cover 8, isolating the oil supply channel 9 from reservoir 7, rocks, underlying oil-saturated formations, or crystalline foundation 10, horizontal wells 11 (figure 3).

 The technology of opening the oil supply channel and its operation are as follows.

1) Establishment of the position of the oil supply channel by the following main features:
- abnormally high oil production rates in production wells from the productive horizons of the sedimentary cover throughout the life of the reservoir and (or) at a late stage (at the final stage of stabilization of oil production);
- low water cut of products;
- high oil production in wells, after their reconnection (after a relatively short period of conservation);
- the lowest level of VNK (in case of distortion);
- zones of increased fracture in the foundation;
- the highest quality of oil (low density, viscosity, paraffin, resin) in producing wells (at the final stage of stabilization of oil production).

 2) Drilling a well with opening horizons, underlying oil-saturated formations, or basement rocks.

 3) Drilling a series of horizontal shafts around the circumference of the bottom.

 4) Isolation of the oil supply channel from the overlying oil-saturated rocks of the trap by injection through the side trunks of an insulating substance (cement or its liquid analogues easily penetrating into the rock) (Figs. 2, 3).

 5) Deepening the well by 20-40 m and testing it in the traditional way.

 Production wells drilled by the proposed method can be exploited significantly (tens of times) longer than conventional ones when extracting oil from a trap. No need to pump large volumes of water. Oil from oil supply channels is lighter and less viscous than in deposits. The operation of oil supply channels in single wells at any (developed and undeveloped) fields, regardless of their reserves, can be economically viable.

 There is an opportunity to develop oil supply channels of small deposits of oil reserves, oil inflow on which (flow rate of the channel) can be very high. In some fields, the oil supply channels ceased to be active (lost contact with the deep reservoir) due to oxidation and an increase in the viscosity (bituminization) of oil in the inflow zone. And in cases of the active existence of the channel and in its passive state, it can be affected in order to activate and increase their flow rate by some of the traditional methods of stimulating the formation in order to increase oil recovery.

 Currently, more than 60% of all open oil fields in Russia are not developed due to economic unprofitability. Under each such field there is an oil supply channel, the flow rate of which is currently unknown. There is no direct connection between the size (reserves) of the field and the intensity of oil inflow through the channel. High debit oil supply channels can be found under some small deposits.

Claims (6)

 1. The method of oil production, which consists in drilling a well and subsequent drilling horizontal wells from its trunk, testing, characterized in that oil production is carried out directly from the oil supply channel connecting the oil reservoir to the deep reservoir, for which the position of the oil supply channel is preliminarily determined, then drilled a well with opening rocks underlying the oil-saturated formations, then, around the circumference from the bottom below the bottom of the oil-saturated formation, horizontal trunks are drilled, through which dissolved insulating material, whereupon the hole deepens and carried her test.  2. The method according to p. 1, characterized in that the position of the oil supply channel is determined by previously conducted field studies of wells producing oil from the productive horizons of the sedimentary cover.  3. The method according to p. 1, characterized in that the position of the oil supply channel is determined by previously conducted geophysical studies.  4. The method according to p. 1, characterized in that the well is deepened to a depth of 20-40 m below the bottom of the oil-saturated formation.  5. The method according to p. 1, characterized in that the well is drilled to the surface of the crystalline basement.  6. The method according to p. 1, characterized in that the well is deepened to a depth of 20-40 m below the surface of the crystalline basement.

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