RU2327726C2 - Thin clay drilling mud - Google Patents

Abstract

FIELD: well drilling; drilling mud.

SUBSTANCE: thin clay drilling mud contains, in mass percent: 2.0-3.0 of bentonitic clay, 0.1-0.15 of carboxymethyl cellulose, 1.0-2.0 of starch, 1.0-5.0 of the reagent for resistivity control - propylene pentamers, 5.0-8.0 of carbonate weighting agent,0.1-0.5 of lubricating additive Lubriol W, remaining - water.

EFFECT: solution quality is improved due to increased resistivity at high temperature while positive filtration, structural-mechanical and rheological properties of solution are preserved.

2 tbl

Description

The invention relates to the field of drilling, namely, water-based drilling fluids used for drilling productive formations and geophysical studies of oil and gas wells.

Clay drilling is complicated by the fact that the increased content of clay particles in the drilling fluid can lead to adhesive interaction with the surfaces of the walls of the barrel and drill pipes and, as a result, to various complications of the drilling process, as well as to a deterioration in the quality of opening of reservoirs. Drilling on low clay drilling fluids improves the performance of bits and generally improves the technical and economic performance of drilling. At the same time, due to the simple decolmation of the reservoir, using acid treatment, it is possible to better maintain the reservoir characteristics of the reservoir, reduce the development time and increase the productivity of the wells.

The disadvantage of low-clay drilling fluids is their low sedimentation stability, especially at elevated temperatures, and high water loss, which negatively affects the state of reservoirs of productive formations, reducing their productivity.

When conducting geophysical studies in the well, it is necessary that the resistivity of the drilling fluid in the well be at least 0.2 Ohm · m. Otherwise, it is impossible to carry out logging methods, which leads to a significant loss of information and makes it difficult to issue a conclusion about the presence of reservoir rocks in the section and the nature of their saturation. The electrical resistivity in a solution is determined by the concentration of salts in the solution, their chemical composition and temperature. With increasing temperature, the mobility of ions increases, which leads to a decrease in the specific electrical resistance.

In addition, when drilling productive rocks, more stringent requirements are imposed on the drilling fluid to limit the filtration of the drilling fluid into the formation and the quality of the filtrate, which would minimize the initial oil permeability of the formation.

A well-known drilling fluid, close in technical essence to the proposed one, containing bentonite clay, ligno-sulfonate thinner, heat-resistant acrylic copolymer, ammonium salt of phosphoric acid and water (RF patent No. 1451155 from 08.10.86). Drilling mud is classified as clayey and has a specific electrical resistivity value at elevated temperatures above the recommended values required for geophysical surveys. A disadvantage of the known drilling fluid is the high values of the filtration rate, which does not allow its use in productive reservoirs.

Known drilling fluid, similar in composition to the proposed and taken as a prototype. The drilling fluid includes a composition of reagents aimed at reducing the filtration coefficient and increasing the recovery coefficient of oil permeability, containing clay, starch, CMC, mineralizer and fresh water, additionally contains calcium carbonate, and mineralized formation water with a density of 1 as a mineralizer , 10-1.16 g / cm ³ total mineralization 180-250 g / l (RF patent No. 2103312 from 01/27/98). A disadvantage of the known drilling fluid is the low electrical resistivity due to the high salt content in the solution, which makes it impossible to conduct electrical logging studies. The purpose of the invention is to improve the quality of the solution by increasing the electrical resistivity at elevated temperature while maintaining the positive filtration, structural-mechanical and rheological properties of the solution.

This goal is achieved in that the low-clay drilling fluid for drilling productive formations and geophysical studies of oil and gas wells contains bentonite clay, carboxymethyl cellulose thermostable, starch, a reagent for regulating electrical resistivity and water, characterized in that as a reagent for regulating specific electrical resistivity contains propylene pentamers and additionally contains a carbonate weighting agent, a lubricant additive with the following content of components, wt.%:

Clay bentonite 2.0-3.0 Thermostable Carboxymethyl Cellulose 0.1-0.15 Starch 1.0-2.0 Propylene Pentamers 1.0-5.0 Carbonate weighting compound 5.0-8.0 Lubricant additive 0.1-0.5 Water Rest

The introduction of propylene pentamers leads to an increase in the electrical resistivity index and a decrease in the filtration index due to partial emulsification of the aqueous phase, while the structural-mechanical and rheological properties of the solution do not deteriorate. The specified reagent is well combined with all functional additives included in the drilling fluid.

To obtain the necessary properties that meet the task, reagents were selected in such a way that, at their minimum content, in combination with other reagents, a synergistic interaction was observed, due to which a solution was obtained with the desired stable properties at elevated temperature.

The reagents that make up the inventive drilling fluid, provide him with the following properties:

- bentonite clay is used as a builder and a regulator of the thixotropic properties of the drilling fluid (increasing retention and transporting ability);

- thermostable carboxymethyl cellulose provides a decrease in the filtration rate while stabilizing and regulating the rheological parameters of the drilling fluid, and gives heat and salt resistance.

The encapsulating properties of the reagent inhibit clay swelling, reduce the accumulation of solid phase in the solution and help to stabilize the walls of the well.

- Starch provides an effective reduction in mud filtration.

- Propylene pentamers increase the electrical resistivity, partially hydrophobize the rock, while facilitating the flow of oil.

- To increase the density of the drilling fluid, a calculated amount of acid-soluble carbonate weighting agent (for example, finely divided chalk) can be introduced into it,

- To improve lubricity in order to prevent sticking of the drilling tool, lubricant is introduced into the drilling fluid.

The achieved effect is ensured by the complex effect of all the components that make up the inventive low clay drilling mud.

From the current level of technology, we do not know that the components that make up the inventive low clay drilling mud in this combination provide the above properties, which allows us to conclude that the proposed technical solution meets the criterion of "inventive step".

In the preparation of the inventive low clay drilling mud in laboratory conditions, the following substances were used:

- Bentonite clay grade PBMB or PBMV manufactured by the company OJSC "Khakassky Bentonite" (TU 39-0147001-105-93);

- Carboxymethyl cellulose of the Carboksil THM-S brand manufactured by Lamberti (Italy);

- Chemically modified starch PSB (TU 6-55-221-1477-97);

- Chalk technical production of JSC "Building Materials", Belgorod (TU 21-020350-06-92);

- Propylene Pentamers produced by OAO Nizhnekamskneftekhim (TU 2211-020-05766801-2003);

- Lubriol lubricant additive brand W (TU 2458-001-74138808-06) manufactured by LLC Techmash, Moscow;

- The water is fresh.

A method of preparing a low clay mud is as follows. For example, to prepare 1000 g of a solution, it is necessary to add 20 g of bentonite clay to 500 ml of water with stirring and allow exposure to swell. The polymer components of the drilling fluid are dissolved in a separate container, for this, with vigorous stirring using a mechanical stirrer, 1 g of carboxymethyl cellulose and 20 g of starch are successively added to 349 ml of water. Stirring is carried out until the reagents are completely dissolved. Then, the prepared polymer solution is introduced into the prepared clay solution and, with stirring, 60 g of chalk and 50 g of propylene pentamers are added. Stir the solution for 20-40 minutes and determine the characteristics of the prepared low clay drilling mud.

Similarly prepare solutions with different proportions of components.

In the laboratory, studies were conducted to determine the technological parameters of the inventive drilling fluid in comparison with the prototype. The main parameters were measured in freshly prepared drilling fluids and after soaking them at a temperature of 80 ° C for 12 hours.

Evaluation of the main technological parameters of the studied fluids was carried out using standard instruments according to the methods described in RD 39-00147001-773-2004 “Methods for monitoring the parameters of drilling fluids”, developed at OAO NPO Burenie. The electrical resistivity was determined using an OFITE resistance meter (OFI Resistivity Meter).

Table 1 shows the data on the component composition of the studied solutions, table 2 shows the technological characteristics of these solutions. The research results show that the proposed drilling fluid can achieve the objectives of the invention.

A comparative analysis of the characteristics of the inventive low clay drilling mud with the prototype shows that the inventive solution has higher values of specific electrical resistivity, which allows it to be used for geophysical studies of wells, and its filtration characteristics (water loss) are much lower, which leads to the preservation of reservoir properties of the formation and predetermines the high efficiency of its use in fishing conditions.

Table 1 The composition of the clay mud Name of components Concentration, wt.% Prototype Solution No. 1 Solution No. 2 Solution No. 3 Solution No. 4 Solution No. 5 Solution No. 6 Clay bentonite 3.0 2 2 one 2 2,5 3.0 Carboxymethyl cellulose 0.7 0.15 0.1 0.1 0.1 0.1 0.1 Starch 0.8 1,0 1,5 2 2 2 1,0 Propylene Pentamers - 2.0 5,0 5,0 3.0 4.0 1,0 a piece of chalk 6.0 6.0 7.0 6.0 6.0 5,0 8.0 Lubricant additive - 0.5 0.15 0.1 0.4 0.5 0.1 Mineralized water 180 g / l 12 - - - - - - Fresh water 77.5 88.35 84.25 84.8 86.5 85.9 86.8

table 2 Technological characteristics of a clayey drilling mud  The name of indicators The value of indicators Prototype Solution No. 1 Solution No. 2 Solution No. 3 Solution No. 4 Solution No. 5 Solution No. 6 Source After exposure at T = 80 ° C Source After exposure at T = 80 ° C Source After exposure at T = 80 ° C Source After exposure at T = 80 ° C Source After exposure at T = 80 ° C Source After exposure at T = 80 ° C Source After exposure at T = 80 ° C Density, g / cm ³ 1.09 1.09 1,073 1,073 1,075 1,075 1,068 1,068 1,055 1,055 1,045 1,045 1,085 1,085 pH 7.0 7.0 9.0 9.0 9.0 9.0 9.0 9.0 9.0 9.0 9.6 9.6 9.9 9.9 Conditional viscosity, s 28 25 36 31 33 thirty 32 thirty 35 31 34 thirty 32 27 Plastic viscosity, MPa · s 25.3 21.1 17.5 16.3 19 17.3 fifteen 13.6 17 14.1 19.5 19.5 20.1 17.1 Dynamic shear stress, dPa 54.8 51.6 66.8 61.6 68 65 64.5 61.3 66.5 62.3 76.5 70,4 77.8 72.3 Static shear stress 1/10, dPa 4.7 / 6.0 0/0 3.3 / 15.8 2.3 / 12.8 1/14 0/9 0/10 0/7 2.5 / 18.5 1.0 / 18.5 2.5 / 20.5 1.7 / 17.3 4.0 / 19.1 2.5 / 11.3 Water loss, cm ^3/30 min 5,0 8.0 4,5 5,0 4.0 4,5 4.0 4,5 4.0 5,0 4.0 5,0 5,0 5.5 The thickness of the peel, mm 1,5 1,5 0.5 0.5 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.5 0.5 Electrical resistivity, Ohm / m 0.15 0.10 5.1 4.9 5,0 4.9 4.4 4.1 5,0 4.6 5,0 4.1 2.7 2.1

Claims (1)

A low-clay drilling fluid for drilling productive formations and geophysical studies of oil and gas wells, containing bentonite clay, thermally stable carboxymethyl cellulose, starch, a reagent for regulating electrical resistivity, a carbonate weighting agent and water, characterized in that it contains a reagent for regulating electrical resistivity pentamers of propylene, as a lubricant additive Lubriol W in the following ratio of ingredients, wt.%: Clay bentonite 2.0-3.0 Carboxymethyl cellulose 0.1-0.15 Starch 1.0-2.0 Propylene Pentamers 1.0-5.0 Carbonate weighting compound 5.0-8.0 Lubriol W lubricant additive 0.1-0.5 Water Rest