RU2229495C2 - Drilling mud - Google Patents

Abstract

FIELD: drilling fluids. SUBSTANCE: water-based drilling mud for making horizontal holes containing, wt %: mud powder 2.0-2.5, chalk 4.0, polyanionic cellulose 1.0-1.2, potash alum 0.15-0.25, and hydrolyzed polyacrylonitrile 0.08-0.10 contains additionally organosilicon liquid 0.10-0.15 and potassium chloride 3.0-3.5. EFFECT: improved quality of drilling mud due improved rheological properties thereof: nonlinearity index and rheological criterion with the aid of easily accessible and environmentally safe reagents. 1 tbl

Description

The invention relates to the field of well drilling, and in particular to compositions of drilling fluids intended for horizontal wells.

To achieve improved drilling performance and successful drilling of a horizontal well, it is especially important to maintain high weighing and bearing properties of the drilling fluid. These requirements are met if a drilling fluid is used in which, after circulation, a structure is formed that is sufficient to hold the slurry in suspension. Such a drilling fluid is characterized by low values of non-linearity indicators (pseudoplasticity, n <0.65) and high values of the rheological criterion (K _p = 300 s ^-1 and higher).

Known drilling fluids with good rheological properties, intended for opening productive formations, including clay, hydrolyzed polyacrylonitrile "uniflock", sodium tripolyphosphate and water [RF Patent No. 2012586, cl. C 09K 7/02, 05/15/94] or clay, starch, carboxymethyl cellulose, calcium carbonate, mineralized formation and fresh water [RF Patent No. 2103312, cl. C 09 K 7/02, 01/27/98].

The use of these drilling fluids for drilling horizontal wells is impossible due to insufficient weighing and bearing capacity.

Closest to the claimed purpose and combination of essential features is a drilling fluid for horizontal wells, containing chalk, a builder, polymer and water [RF Patent No. 2087516, cl. C 09 K 7/02, 08/20/97]. The structure-forming agent in this drilling fluid is a mixture of short-fiber chamber grade asbestos, grade K-6-30, and exola (a mixture of saturated and unsaturated alcohols).

However, this technical solution has the following disadvantages: the complexity and duration of the process of modifying asbestos with exol, the selection of only a specific brand of asbestos and unsafe for the health of working personnel, insufficiently high bearing and weighing properties.

The technical result of the invention is to improve the quality of the drilling fluid by improving its rheological parameters: an indicator of non-linearity and rheological criteria using readily available and environmentally friendly reagents.

A drilling fluid for drilling horizontal wells containing water, chalk, a structuring agent and hydrolyzed polyacrylonitrile “uniflock” contains clay powder, PAC-B polyanionic cellulose and alum-potassium alum, and additionally, organosilicon liquid and potassium chloride in the following ratio of components, wt.% : clay powder 2.0-2.5; chalk 4.0; PAC-B polyanionic cellulose 1.0-1.2; potassium alum 0.15-0.25; hydrolyzed polyacrylonitrile “uniflock” 0.08-0.10; organosilicon liquid 0.10-0.15; potassium chloride 3.0-3.5, water - the rest.

From the patent and scientific and technical literature, we do not know drilling fluids containing a combination of the above components in the proposed quality ratio, which allows us to conclude that the claimed technical solution is new.

The technical result achieved by the invention is that a composition consisting of a clay suspension, polyanionic cellulose and alum-potassium alum gives the drilling fluid high dynamic shear stresses at relatively low plastic viscosity values.

In the process of dispersing clay powder in water due to metabolic processes in the crystalline structure of clay particles and the transition of aluminum ions into an active form, they form a strong bond with the polyanionic cellulose molecule. At the same time, potassium alum "crosslink" the polyanionic molecules PAC-B, forming a strong gel-like structure in the drilling fluid. As a result, a “cross-linked” composition is formed in the drilling fluid: a clay particle, a polymer molecule — aluminum ions (potassium alum), whose structure-forming ability is not inferior to foreign-made biopolymers.

From the existing level of technology, we do not know that this composition in the drilling fluid provides the above properties, which allows us to conclude that the proposed technical solution meets the criterion of "inventive step".

It is known from scientific, technical and reference literature that components such as HCL and potassium chloride inhibit and hydrophobize clay particles of the formation, which ultimately reduces the likelihood of complications of a deformation nature and softening of the walls of the well.

If necessary, the required amount of lubricant can be added to the drilling fluid.

The solution is prepared as follows.

In one phase, the clay powder is dispersed. Then add the calculated amount of PAC-B and Uniflock and mix thoroughly until the polymers dissolve. Potassium alum is added to the resulting polymer-clay composition in the form of a 10% aqueous solution. The composition is mixed until a crosslinked structure is formed in the solution, which is fixed by increasing the viscosity of the solution. KC1, GKZH, chalk are successively added to the structured solution, and they are intensively mixed after adding each reagent and until a homogeneous mass is formed.

An example of the preparation of a drilling fluid (composition No. 2).

20 g of clay powder are dispersed in 880 ml of industrial water, then 12 g of PAC-B and 1.0 g of Unifloc are added to the clay suspension and mixed until the polymers dissolve. 15 ml of a 10% aqueous solution of alum-potassium alum are added to the obtained polymer-clay composition and mixed until a crosslinked structure is formed in the solution. 30 g of KCl are added to the resulting solution with vigorous stirring, after it is dissolved, 1.5 g of HCL, and then 40 g of chalk. Stirring is continued until a homogeneous mass is formed. The solution is left for 1-2 hours, then, after thorough mixing, the technological parameters of the drilling fluid are measured by standard methods.

Similarly prepare solutions with different proportions of components.

The composition and technological parameters of the inventive drilling fluid and the solution of the prototype are presented in the table.

As can be seen from the table, the drilling fluid for drilling horizontal wells allows you to achieve the objectives of the invention. The non-linearity indices of the proposed solutions are close to the non-linearity index of the prototype solution (n <0.65). High values of the rheological criterion (1.63-2.60 times higher than that of the solution of the prototype) indicate a high load-bearing and weighing ability of the inventive drilling fluid. At the same time, all other technological parameters of the drilling fluid satisfy the requirements for high-quality drilling through horizontal drilling.

2 horizontal wells were drilled at the Ravenna field 000 LUKOIL-Western Siberia using the proposed drilling fluid compositions with horizontal boreholes in productive formations of 500 m. Both wells were drilled without complications, with high mechanical speed and opening quality of the productive stratum. Wells were commissioned in a fountain way.

The obtained results of field tests showed that the proposed drilling fluids are of high quality and can achieve this goal.

Legend: ρ - density; T - conditional viscosity; F - filtering; СНС - static shear stress; K is the thickness of the peel; φ is the coefficient of friction; η _PL - plastic viscosity; τ ₀ - dynamic shear stress; pH is a hydrogen indicator; n is the nonlinearity index; To _p - rheological criterion.

Claims (1)

A drilling fluid for horizontal wells, containing water, chalk, a structuring agent and hydrolyzed polyacrylonitrile “uniflock”, characterized in that it contains clay powder, PAC-B polyanionic cellulose and alum-potassium alum, and additionally an organosilicon liquid and potassium chloride as a structuring agent components, wt.%: Clay powder 2.0 - 2.5 Chalk 4.0 PAC-V polyanionic cellulose 1.0 - 1.2 Alum potassium alum 0.15 - 0.25 Hydrolyzed Uniflock Polyacrylonitrile 0.08 - 0.10 Silicone fluid 0.10 - 0.15 Potassium chloride 3.0 - 3.5 Water Else