RU2540713C1 - Method of oil pool development - Google Patents

Abstract

FIELD: oil-and-gas industry.

SUBSTANCE: in compliance with this process, working fluid is injected via injection wells. Oil is extracted via production wells to effect primary and secondary hydro frac in wells. At secondary hydrofrac seams are perforated at density of at least 10 bores per running meter of hydrofrac interval. Proppant is injected in amount of at least 10% larger than that at primary hydro frac. Final concentration of proppant is increased as compared with primary hydrofrac by at least 10%. Volume of polymer gel-forming agent as compared with primary hydrofrac is decreased by at least 10%.

EFFECT: higher efficiency of secondary hydro frac.

3 ex, 1 tbl

Description

The invention relates to the oil industry and may find application in the development of oil deposits.

There is a method of improving the hydrodynamic connection of a well with a reservoir, including acid hydraulic fracturing (Fracturing) by installing a packer over the roof of a perforated reservoir, injecting frac fluid into the sub-packer zone, creating fracture pressure in the sub-packer zone and squeezing the fracture fluid into the crack. After acid fracturing, repeated fracturing is performed in two stages. At the first stage, the crack formed due to acid fracturing is fixed by injection of hydraulic fracturing fluid with proppant in an estimated amount sufficient to change the horizontal stresses in the carbonate formation and ensure the perpendicular direction of the second fracture formed during the second stage of acid fracturing relative to the first fracture. After the first stage of repeated hydraulic fracturing, the well is poured into the spout through the fittings in an increasing sequence of their diameters. At the first stage of hydraulic fracturing, a gel is used as a hydraulic fracturing fluid, and at the second stage, an acid composition is used (RF patent No. 2462590, published. 09.27.2012).

Closest to the proposed invention in technical essence is a method of developing an oil and gas reservoir using hydraulic fracturing, which includes carrying out the first stage of hydraulic fracturing in all production wells. At the same time, using geophysical methods based on registration of microseismic vibrations, as well as on registration by downhole dipsticks, changes in the dip angle of the formations that occur during hydraulic fracturing, determine the direction of the development of hydraulic fractures in azimuth. When production wells decrease below 10% of the initial values, hydraulic fracturing is carried out in all injection wells, and immediately after hydraulic fracturing in injection wells, the formation is treated with high pressure to increase injectivity. When the production rates of production wells fall by more than 50% from the initial values, they perform repeated hydraulic fracturing (RF patent No. 2496001, published on October 20, 2013 - a prototype).

A common disadvantage of the known methods is the low efficiency of repeated (secondary) hydraulic fracturing.

The proposed invention solves the problem of increasing the effectiveness of repeated hydraulic fracturing.

The problem is solved in that in the method of developing an oil reservoir, which includes injecting a working agent through injection wells, taking oil through production wells and conducting primary and repeated hydraulic fracturing in wells, according to the invention, with repeated hydraulic fracturing, perforation of formations with a density of at least 10 holes per linear meter is performed fracturing interval, proppant mass is pumped by at least 10% more proppant mass during primary fracturing, the final proppant concentration is increased by at least 10% in comparison with primary hydraulic fracturing, and in comparison with primary hydraulic fracturing, gel builder load is reduced by no less than 10%.

SUMMARY OF THE INVENTION

When developing an oil field, the production rate and injectivity of wells are inevitably reduced. One of the most effective ways to increase well productivity is hydraulic fracturing. However, even after hydraulic fracturing, the decline in well productivity continues. With a decrease in productivity, repeated hydraulic fracturing is carried out in the same wells and in the same intervals of the productive formations. However, the effectiveness of repeated hydraulic fracturing is low. The proposed invention solves the problem of increasing the effectiveness of repeated hydraulic fracturing. The problem is solved as follows.

With repeated hydraulic fracturing, repeated perforation of formations with a density of at least 10 holes per linear meter of the hydraulic fracturing interval is performed, proppant mass is pumped by at least 10% more proppant mass during primary hydraulic fracturing, the final proppant concentration is increased by at least 10% in comparison with primary hydraulic fracturing, reduce the load of the gelling agent in comparison with primary hydraulic fracturing by at least 10%.

As a rule, the larger the load of the gelling agent, the greater the precipitation, a decrease in the load of the gelling agent, starting from a load of 4 kg / m ³ for every 0.1 kg, gives a decrease in precipitation by an average of 0.5%.

Concentrated liquids have their own advantages, for example: a liquid with a concentration of 4 kg / m ³ hydrates faster than a liquid with a concentration of 3.6 kg / m ³ , but there is a side effect: when the polymer is decomposed, a non-decomposing residue remains depending on the concentration of the gel-forming agent (ratio of 100 g of gel-forming agent adds an average of 0.5% undecomposed residue). Sediment acts on the formation as a plugging material or as a grouting material in the pore space of the formation.

If we take as a base a gelant load of 4 kg / m ³ with an average sedimentation for a fracture fluid of 10-20%, then if the polymer load decreases to 3.6 kg, the precipitation will decrease by an average of 2%.

All these modes together change and increase the geometry of the fixed crack — new zones open, deviation and partial reorientation of the crack occur, and the drainage area changes. Also, the quality of the fracturing fluid has a great influence on repeated fracturing. It is necessary to use a more modern fracturing fluid - with a lower concentration of gelling agent to reduce sedimentation.

Concrete example

Example 1 (prototype). An oil reservoir is being developed with productive formations D1a and D1b3 in the intervals of 1642-1644 m, 1654-1656 m.

Selected reservoir products through production wells and injected working agent - produced water through injection wells.

Intensify the operation of an oil well. The well was put into operation with an initial flow rate of 4 m ³ / day and a water cut of 18%. Lithology of objects: the upper layer D1a - clay sandstone (absolute permeability 338.5 mD, porosity 16.7%, clay 2.0%); the lower layer D163 - clay sandstone (absolute permeability 731.1 mD, porosity 22%, clay 3.5%).

The design of the well and the flat equipment production casing with a diameter of 146 mm is tight.

Primary fracturing

The column of tubing is lowered, the face is poured with a sand bridge to a depth of 1661.7 m.

The packer is lowered on a tubing string with a diameter of 89 mm to a depth of 1633 m and the packer is planted.

The fluid flow rate to hydraulic fracturing is 4 m ³ / day, and the oil flow rate is 3 tons / day. The hydraulic fracturing was carried out with the injection of 8000 kg of proppant (fraction 16/30 mesh - 6000 kg, fraction 12/18 - 2000 kg), fracturing fluids 73 m ^{3 were used} , gel load was 4.2 kg / m ³ , final concentration 370 kg / m ³ .

According to the results of processing the results of recording the wellhead pressures of the hydraulic fracturing, the following data were obtained: fixed crack length (one wing) - 23.6 m; the crack height created - 14.08 m, fixed - 1.78 m. The width of the crack after relieving pressure on the formation is 0.88 mm, the maximum width of the crack at the perforation intervals is 7.04 mm, and the conductivity of the crack is 478.3 mD / m. According to the results of hydraulic fracturing, an average daily increase in oil of 2.5 tons / day was obtained.

In the process of operation after the first hydraulic fracturing, a gradual decrease in flow rate occurred over 3 years. Oil production rate decreased from 9 tons / day (after the first hydraulic fracturing) to 3 tons / day.

Repeated hydraulic fracturing according to technology and modes in accordance with the first hydraulic fracturing.

Example 2. Perform as example 1.

Perform primary hydraulic fracturing, as in example 1. After reducing the flow rate to 3 tons / day, repeat hydraulic fracturing is performed according to the following technology of the regime.

In the intervals of hydraulic fracturing 1654-1656 m, 1642-1644 m spend cumulative perforation in the amount of 40 holes - with a density of 10 holes per linear m.

The column of tubing is lowered, the face is poured with a sand bridge to a depth of 1658 m.

The packer is lowered on a tubing string with a diameter of 89 mm to a depth of 1633.2 m and the packer is planted.

Perform a test download. The initial injectivity of the fracturing object Q-240 m ³ / day, the initial pressure Pnach = 11 MPa, the final pressure Pkon = 11 MPa. The quality of communication with the formation is determined by injecting 5 m ^{3 of} technical fluid with a density of 1.18 g / cm ³ without preliminary saturation of the bottomhole zone.

During hydraulic fracturing, technical water samples are taken and analyzed for the content of mechanical impurities, the content of free hydrogen ions and temperature, test preparation of the fracturing fluid is carried out, a test for dissolution and crosslinking is performed. The results are satisfactory. A gel is prepared in a volume of 25 m ³ based on a WG 46 Econotec gelling agent based on guar gum (manufactured by Economy Polymers & Chemicals). Rheology - temperature 27 ° C, viscosity 21 cP, crosslinking time 4 sec. A demulsifier, a degradation activator and a clay stabilizer are added to the gel, the mixture is brought to a homogeneous state with stirring, and the pressure pumps are started and heated.

A test injection is performed with recording the pressure drop and processing the obtained data on the pressure drop - in the volume of 25 m ^{3 of the} fracturing fluid with the addition of 1000 kg of proppant fraction 20/40. The test pack passed the perforation interval with increasing pressure from 22 MPa to 24 MPa. The data obtained are processed, data are obtained on the performance of the fracturing fluid, the value of the net pressure, the stress gradient in the formation, the time and pressure to close the fracture, the pore pressure in the reservoir, hydraulic pressure losses in the perforation interval and the bottom of the formation. Based on the data obtained, the design data of the fracturing process are adapted to the received test injection processing data. The main hydraulic fracturing process is carried out.

Corrected data is used to re-calculate the three-dimensional fracturing model and refine the fracturing plan. Based on the calculations made, a set of the required volume of the process fluid is prepared and a fracture fluid is prepared with testing. The test results are satisfactory. The hydraulic fracturing process is carried out in accordance with the updated plan, the fracturing fluid is prepared with a gelling agent 3.4 kg / m ³ and with a proppant concentration in stages: 120 kg / m ³ , 200 kg / m ³ , 250 kg / m ³ , 300 kg / m ³ , 350 kg / m ³ , 400 kg / m ³ , 500 kg / m ³ , 600 kg / m ³ . 700 kg / m ³ , 800 kg / m ³ to improve the hydrodynamic connection of the formation with a fracture.

The final proppant concentration is 800 kg / m ³ , which corresponds to 216% of the final proppant concentration during the first hydraulic fracturing.

The load of the gelling agent is 3.4 kg / m ³ , i.e. it is reduced by 19%.

The pressure at the wellhead is the initial 22 MPa, the final 27 MPA, where the volume of the final push is defined as the sum of the volume of the tubing string and sub-packer zone to the roof of the perforation interval minus the volume of the estimated undersupply. The working flow rate for the main process is 3.3 m ³ / min. At the end of the proppant-gel mixture sale, the pumping units are stopped and the pressure drop recorded, after which the wellhead is closed, the equipment is dismantled and the well is left to wait for the pressure drop. At the end of the necessary time for the destruction of the gel, the residual wellhead pressure is vented to atmospheric pressure. The start of overpressure release is carried out after 12 hours. The wellhead is depressurized, stalling and lifting of packer equipment is performed.

Based on the results of processing the results of recording the wellhead pressures of the performed process, the following data were obtained: fixed crack length (one wing) - 64.68 m; crack height created - 15.04 m; fixed - 9.34 m. The width of the crack after relieving pressure in the formation is 2.7 mm; the maximum width of the crack at perforation intervals is 14.1 mm; crack conductivity 622.8 mD / m. The injected proppant has a mass of 10,000 kg (20/40 - 1,000 kg, 16/30 - 6,000 kg, 12/18 - 3,000 kg), which is 25% higher than in the previous treatment.

Example 3. Perform as example 2.

In the intervals of hydraulic fracturing of 1654-1656 m, 1642-1644 m, cumulative perforation is carried out in the amount of 48 holes - with a density of 12 holes per linear m. The total amount of proppant is 8.8 tons, which is 10% more than in the previous treatment. Increase the final proppant concentration by 10% to 410 kg / m ³ . At the same time, the load of the gelling agent - WG - 40 DS based on hydroxypropylguar (manufactured by Economy Polymers & Chemicals) is reduced by 10% to 3.7 kg / m ³ .

The well was put into operation 19 days after the completion of hydraulic fracturing with an increase in productivity more than 4 times without an increase in water cut. The average daily increase in oil amounted to 6.7 tons / day, more than 2 times higher than the indicators from the first hydraulic fracturing.

Example 4. Perform, as example 2. As a gelling agent use GPG-3 - a polysaccharide according to TU 2499-072-17197708-2003 (manufacturer ZAO Petrohim).

A comparative analysis of the proposed method and prototype are presented in table 1.

The table below shows the parameters for the well with hydraulic fracturing with a time difference of four years. As can be seen from the table, there are differences in the modes of hydraulic fracturing in one well during primary and repeated hydraulic fracturing. The proposed hydraulic fracturing is carried out with a proppant amount of 25% greater than in hydraulic fracturing according to the prototype, the final concentration is also higher. In the proposed hydraulic fracturing, a fracturing fluid with a lower specific quantity of polymers is used - the gel builder load is reduced from 4.2 to 3.4 kg / m ³ , which allowed to reduce sedimentation. As a result, the crack has a large length, fixed height and width. A change in geometry made it possible to obtain a more conductive crack, and a decrease in the amount of gelling agent made it possible to reduce sedimentation. Ultimately, the average daily increase in oil by the proposed method is more than 30% higher than the hydraulic fracturing performance of the prototype without increasing water cut. Thus, the proposed method allows to increase the efficiency of hydraulic fracturing by changing the geometry of the fracture, the distribution of proppant in the reservoir and the use of more advanced fracturing fluids.

Claims (1)

A method of developing an oil reservoir, including pumping a working agent through injection wells, taking oil through production wells and conducting primary and repeated hydraulic fracturing in the wells, characterized in that during repeated hydraulic fracturing, the formation is perforated with a density of at least 10 holes per running meter of the hydraulic fracturing interval, proppant mass is pumped by at least 10% more proppant mass during the initial hydraulic fracturing, the final proppant concentration is increased in comparison with the primary g drorazryvom formation to not less than 10%, and the volume loading of polymeric gelling agent in comparison with a primary hydraulic fracturing is reduced by at least 10%.