RU2278890C1 - Drilling mud for exposing producing formation with low formation pressions - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: invention, in particular, relates to clayless drilling mud used for boring and completion of wells, including horizontal ones and offshoots, which drilling mud 0.2-0.25% bactericide (LPE-11), 0-0.35% soda ash, 1.5-3.5% starch (FITO-RK), 0.4-0.75% biopolymer (Robus), 1.0-2.0% ferrochromolignosulfonate, and water - the rest.

EFFECT: improved quality of primary exposure of "exhausted" producing oil reservoir having low formation pressions.

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Description

The invention relates to the drilling of oil wells, in particular to clay-free drilling fluids used for drilling and completion, including horizontal and sidetracks.

Clay-free muds based on various polymers are widely used for drilling and well completion. Their main advantage is the absence of a solid (clay) phase in them, which causes the formation of a filter cake, and in a porous medium of a collector - a hard-to-remove zone of mudding. But, on the other hand, the absence of a clay crust when using a clayless polymer solution leads to the penetration of large volumes of filtrate into the reservoir, which causes a significant increase in the water saturation of the bottom-hole zone of the reservoir and a decrease in the phase permeability for oil.

For high-quality opening of productive formations, the type of polymer used as the polymer base for the preparation of clay-free polymer solution (BPR) is of great importance. Initially, acrylic (PAA, hypane, metas, HP, etc.) and cellulose-containing (CMC, OEC, PAC, etc.) polymers, which are practically not subject to acid and biological degradation, were mainly used for this purpose.

Known emulsion drilling fluid containing a hydrocarbon phase, calcium carbonate, mineral salt, stabilizer and mineralized water containing FITO-RK starch as a stabilizer, magnesium chloride and potassium chloride as a mineral salt, as well as a surfactant of complex action PCD -515 (RF Patent No. 2213761, IPC С 09 К 7/00 of 10/10/2003). Due to the potassium chloride salts contained in the drilling fluid, the solution will have very low electrical resistivity, which will negatively affect the quality of geophysical surveys.

The closest of the analogues (RF Patent No. 2179568, IPC S 09 K 7/00 of 02/20/2002) is a clay-free drilling mud for opening oil wells with low reservoir pressures, containing a polymer base, a lubricating additive, a surfactant and water, according to the invention additionally contains polyglycol and a carbonate weighting agent, starch and biopolymer as a polymer base, and a condensation product of monoethanolamine and crude tall oils mixed with kerosene, monoethanolamine and flotation reagent as a lubricant additive ksalem (DRC-4CT reagent) as surfactant - PAO-515 with the following ratio of ingredients, wt.%:

Starch 1.0-1.5 Biopolymer 0.2-0.3 Polyglycol 3-5 Specified Lubricant Additive 0.5-1.0 Surfactant PKD-515 1.5-2.0 Carbonate weighting compound 5-10 Water rest

The technical result of the present invention is to improve the quality of the primary opening of "depleted" productive reservoirs with low reservoir pressure. This technical result is achieved by the fact that a clay-free drilling fluid for opening oil wells with low reservoir pressures, containing FITO-RK starch, a biopolymer and water, according to the invention, contains a Robus biopolymer as a biopolymer and additionally contains soda ash, LPE-11 bactericide, ferrochromlignosulfonate (FHLS) in the following ratio of ingredients, wt.%:

bactericide LPE-11 0.2-0.25 soda ash 0-0.35 FITO-RK starch 1,5-3,5 Biopolymer "Globus" 0.4-0.75 ferrochrome lignosulfonate (FHLS) 1.0-2.0 water rest

The choice of the inventive starch solution and biopolymer as the polymer base is due to their good acid and biological degradability. In addition, the biopolymer gives the solution pronounced pseudoplastic properties, which contributes to the good removal of cuttings, especially from a horizontal trunk.

FITO-RK starch (TU-2483-002-41668452-97) and the Globus biopolymer (TU 9172-003-35944370-01) manufactured by Promservice CJSC in the Yalchik district of the Chuvash Republic are used as stabilizer and reducing agent for drilling fluid filtration.

To prevent biodegradation of drilling fluid components, to prevent bio-contamination of formations, and to neutralize hydrogen sulfide, the bactericide LPE-11 (TU 6-01-101294949-08-89) manufactured by JSC NPO Technolog, Sterlitamak, is used.

Ferrochromlignosulfonate (FHLS) is designed to control the structural and mechanical properties of drilling fluids (TU 2458-015-20672718-2001), 000 NPV BashInkom, Ufa, are produced.

Soda ash (GOST 5100-85) is used to control the pH of the environment, produced "Soda" Sterlitamak.

From the patent and scientific and technical literature, we do not know the drilling fluid containing the combination of the above ingredients in the proposed quantitative ratio, which allows us to conclude that the claimed invention is new.

A method of preparing a drilling fluid is as follows. For example, 2.5 g of a bactericide, 2.5 g of soda ash, 10 g of PFCs are dissolved in 946 ml of water, then 4 g of biopolymer and 35 g of starch are added with complete stirring.

In laboratory conditions, comparative experiments were conducted with the inventive solution and with the solution adopted as a prototype of the invention (patent No. 2179568). Assessment of the main technological parameters of the studied solutions was carried out using standard instruments and standard techniques (for example, Ryazanov Y. A. Reference on drilling fluids. M .: Nedra, 1979).

Table 1 shows the data on the component compositions of the studied reagents. Solutions 1-5 contain components in the minimum and maximum declared limits.

Table 2 provides information on the technological parameters of the investigated solutions and the prototype solution 6.

A comparative analysis with the prototype allows us to conclude that the inventive solution prevents the penetration of the drilling fluid filtrate into the bottomhole zone of the reservoir, improve the rheological properties, give the solution pseudoplastic properties, and also helps to reduce the density of the drilling fluid (0.88-0.94 g / cm ³ )

To study the process of interaction of natural core samples with this solution, experiments were carried out to simulate the "opening" and "development" of samples of natural terrigenous reservoirs of the Spassky field in compliance with thermodynamic conditions (pressure 12 MPa, temperature 25 ° C).

Preliminary preparation of the samples consisted of their extraction in toluene and alcohol-benzene mixture, drying to constant weight at a temperature of 85 ° C. This achieved the removal from the pore space of hydrocarbons, water and inorganic salts dissolved in water.

In the experiments, reservoir models were used containing two cylindrical rock samples placed in a core holder. Previously, in each sample, the associated water saturation was simulated up to 20%, which corresponds to the actual conditions of the Yugomash-Maksimovskoye field (reservoir water density 1.21 g / cm ³ ). After the preparation of models, an isoviscous degassed oil was pumped through them (viscosity 6.98 MPa · s, density 0.85 g / cm ³ ). The process of opening the reservoir model consisted in pumping several pore volumes of this solution through the model. Then the reservoir model was left in contact with the solution for 8-10 days. At the end of the autopsy operation, oil was pumped again at low speeds in the direction from the reservoir to the well. Duration of pumping was 3-5 pore volumes to stabilize permeability. Thus, the full cycle of operations of opening and mastering reservoir models consisted in displacing oil from the model, first with a solution, then with a solution of oil. In each half-cycle, the permeability coefficient for this phase was determined. Then calculated the recovery coefficient of the initial permeability β according to the formula:

where K _CR1 is the initial oil permeability of the model, K _CR2 is the oil permeability coefficient after modeling the development process.

The experiments were performed on a FDES-645 installation (Cortest, USA) with computer software, which allows simulating the conditions for opening a reservoir and reservoir pressure up to 35 MPa, rock pressure up to 66.5 MPa, reservoir temperature up to 150 ° С. The flow rate of the test fluid is from 0.001 to 10 cm ³ / min.

In the experiments, two reservoir models were used, identical in porosity and air permeability, about 25 cm long. The experimental results are presented in Table 2. As can be seen from Table 2, when modeling the process of opening and mastering the reservoir model, the recovery coefficient β for solutions 4 and 5 was 51 and 81%, respectively.

With these solutions, 3 wells were drilled without complications: No. 5241 of Yugomash-Maksimovskaya area with solution 1, No. 5243 (horizontal) of Yugomash-Maksimovskaya area with solution 2, No. 10323 of Nikolo-Berezovskaya area with solution 4. When testing these compositions, no absorption of the drilling fluid is observed and pollution of productive facilities. The composition of the drilling fluids is stable, fireproof, non-toxic, has good fluidity (pseudoplastics) and is easily pumped by the pump.

Table 1 Solution number The composition of the solutions, wt.% Bactericide LPE-11 Soda ash FITO-RK starch Biopolymer "Globus" FHLS water one 0.25 0.25 3.5 0.4 1,5 94.1 2 0.25 0.25 3,5 0.4 1,0 94.6 3 0.2 0.35 1,5 0.6 2.0 95.35 four 0.2 - 1,5 0.75 1,5 96.05 5 0.2 - 3.0 0.65 1,5 94.65

table 2 Solution number Solution parameters ρ, g / cm ³ F, cm ³ F (0.7 MPa), cm ³ SNA, dPa η _pl , MPa · s τ ₀ , DPa η _pl (Brookf.), MPa · s pH n ρ, Ohm Permeability recovery coefficient,% 1 min 10 min one 0.94 - - 30.31 33.34 21 38 388000 8.4 0.44 - - 2 0.91 - 7.5 39,4 42,4 24 41 410000 8.20 0.45 3,7 - 3 0.92 - - 38,4 53.3 fifteen thirty 413000 8.7 0.41 - - four 0.88 5 - 60.62 63.65 21 fifty 459000 5,4 0.37 2,4 51 5 0.89 5.5 - 36.37 42,43 twenty 42 415000 5,4 0.4 2.7 81 6 1,03 - - 9.2 12,4 - - - - - 2.27 -

Claims (1)

Clay-free drilling fluid for opening oil wells with low reservoir pressures, containing FITO-RK starch, a biopolymer and water, characterized in that it contains a “Rosobus” biopolymer and additionally contains soda ash, LPE-11 bactericide, and FCL ferrochrome lignosulfonate in the following ratio ingredients, wt.%: Bactericide LPE-11 0.2-0.25 Soda ash 0-0.35 FITO-RK starch 1,5-3,5 Biopolymer "Globe" 0.4-0.75 FHLS ferrochrome lignosulfonate 1.0-2.0 Water Rest