RU2276258C2 - Method for hydraulic reservoir fracturing - Google Patents

Abstract

FIELD: oil production, particularly hydraulic reservoir fracturing in oil or oil-and-gas condensate well.

SUBSTANCE: method involves fracturing reservoir with hydrocarbon liquid having similar or the same properties as hydrocarbon liquid to be produced from reservoir; transmitting propane with liquid. The propane is taken as bentonitic or hydrophobizated clay having particle dimensions of 0.1-30 μm taken in amount of 2-5% by weight of hydrocarbon additive to be added in transmission liquid. The transmission liquid includes hydrocarbon additive, namely hydrocarbon solvent taken in amount of 15-30 % by weight, cationic or anionic surfactant in amount of 0.05-0.1% by weight, remainder is water.

EFFECT: increased reservoir liquid inflow to well bottom, increased efficiency, possibility to retain reservoir drainage capacity.

Description

The invention relates to hydraulic fracturing in wells for various purposes and, in particular, in an oil or oil and gas condensate well to increase the influx of volumes of reservoir fluid entering the bottom of this well.

Existing technologies for increasing the volume of formation fluid entering the face are to increase the filtration area, which is realized due to hydraulic fracturing, the essence of which is the formation of cracks in the formation with their subsequent fixation [1].

To ensure proper hydraulic fracturing, for example, oil, create increased pressure at the bottom by pumping hydraulic fracturing fluid into the well.

To fix the fractures formed in the formation rock by fracturing, sorted coarse-grained sand is added to the fracturing fluid, the role of which is to prevent the cracks from closing after the pressure has decreased.

The fracturing fluid must be of high viscosity to hold the sand grains in suspension during the entire technological cycle and should not reduce the hydraulic conductivity of the formation.

As a hydraulic fracturing fluid, aqueous solutions of polymers are usually used (for example, solutions of polyacrylamide or polysaccharide or polyamides).

Sand for filling cracks during hydraulic fracturing must meet the following requirements:

- to have high mechanical strength to form reliable sand cushions that do not collapse under conditions of volumetric compression under the action of pressure of overlying rocks;

- maintain high permeability of formation fluids. Coarse-grained, well-rolled and homogeneous quartz sand with a grain size in the range of 0.5-2 mm meets these requirements.

The known method of increasing the filtration area of the formation fluid according to the aforementioned known method has a number of significant drawbacks, in particular, coarse sand is used, which requires significant energy costs both for the actual fracturing with the required crack size, and for the subsequent introduction of such sand into this crack.

After installing the packer, the entire zone to the bottom, including the oil-saturated stratum, is affected by hydraulic fracturing pressure and can be torn in this interval, and often in the most arbitrary and not always desirable place of this interval

As indicated above, as a rule, a hydrophilic liquid serves as a fluid carrier for supplying quartz sand to the fracturing zone, which enters mainly into water-saturated layers, which are torn. In addition, hydraulic fracturing, falling into newly formed cracks, often reduces the drainage properties of the formation in hydrocarbon fluid, for example, in oil.

Coarse grained sand used for fracturing cannot enter microcracks coming from the main macrocrack.

A known method of hydraulic fracturing, in accordance with which to fix a hydraulic fracture using rubber crumb with a diameter equal to or less than the diameter of the pore channels of the reservoir, while the rubber crumb is delivered to the hydraulic fracturing zone in the form of a suspension in a hydrocarbon fluid, with physico-chemical parameters corresponding to the hydraulic fracturing [2].

The disadvantages of this method include the disadvantages of the previous described method, as well as the fact that the rubber crumb does not have the necessary mechanical strength and, after relieving the hydraulic fracturing pressure, the formed cracks close, which does not provide an increase in the filtration area to the proper extent.

The technical result of the invention is to increase the efficiency of the method of hydraulic fracturing due to the possibility of its implementation in a given interval of the reservoir and the preservation of the drainage properties of the reservoir.

The required technical result is achieved by the fact that the hydraulic fracturing method includes slotted hydraulic jet perforation of the formation and subsequent hydraulic fracturing in the interval of the slotted hydraulic jet perforation, in which case a hydrocarbon fluid similar or identical in its properties to the hydrocarbon fluid extracted from the formation is used.

The essence of the invention lies in the fact that using a preliminary slit hydro-jet perforation, strictly in a predetermined interval of the producing formation, a stress state is created in the formation array. This initiates subsequent hydraulic fracturing in this interval. This solution eliminates the accident of hydraulic fracturing in the undesirable interval of the reservoir, when, for example, a spreading aquifer can be unintentionally opened, which excludes the possibility of subsequent effective well operation. Experience has shown that fixing this error is almost impossible. Any subsequent attempts to re-fracture lead to the usual re-opening of the initially formed crack.

A successful condition for hydraulic fracturing is the use of a hydrocarbon fluid, such as oil, as a working fluid for hydraulic fracturing. Hydrocarbon fluid, similar or identical in its properties to the hydrocarbon fluid extracted from the formation, does not reduce the drainage properties of the reservoir to the produced hydrocarbon fluid.

Does not reduce the drainage properties of the formation and the targeted effect of the forces of dynamic action on this formation in the area of its saturation with a hydrocarbon fluid. This is facilitated by a means for fixing a hydraulic fracture in the form of a hydrophobic proppant, which, under the action of an increased downhole depression, is finally and automatically redistributed and fixed mainly in the interlayers of the considered formation saturated with hydrocarbon liquid.

Particles of bentonite clay with a hydrophobic coating are used as a hydrophobic proppant on their outer surface with transverse dimensions from 0.01 to 3 diameters of the capillaries of the formation, which corresponds to a fraction of particles of bentonite clay of 0.1-30 μm. These particles in the environment of a hydrocarbon fluid fill microcracks from the main macrocrack of hydraulic fracturing with finely divided plugging material, which does not reduce the drainage properties of the formation in hydrocarbon fluid. Particles of bentonite clay can be, when preparing their quality as a proppant, subjected, for example, to firing to increase their strength.

Since the intermolecular adhesion forces between the rock particles are weakened in the presence of a hydrocarbon fluid between them, the efficiency of the hydrocarbon fluid that has fallen into the interlayer saturated with the produced hydrocarbon fluid, such as oil, will be maximum. The physicochemical characteristics of the hydrophobic proppant, including viscosity, are controlled by the corresponding known ingredients.

The method is as follows.

An injection string of pipes, for example tubing, equipped with a packer, is lowered into a well selected for fracturing. The packer is installed on the tubing string with the possibility of bringing it into working position at the level of the roof of the formation or slightly below this roof (in the dense differences of the formation).

Before planting the packer from the tubing and the well, the kill fluid is displaced by the hydrocarbon fluid.

Preparing the propane delivery fluid to the well to consolidate the fracture. As the proppant, hydrophobized bentonite clay particles with a fractional composition of 0.1-30 microns are used.

The propane transportation fluid contains a hydrocarbon solvent, for example, oil, in an amount of 15-30% by weight, a cationic or anionic type surfactant, such as sodium stearate, in an amount of 0.05-0.1% by weight. and water is the rest.

The proppant, for example hydrophobized bentonite clay with a fractional composition of 0.1-30 microns, is 2-5% by weight. the weight of the hydrocarbon base of the liquid in the composition of the liquid for transporting proppant, which is 0.3-1.5% of the weight of the liquid for transporting proppant.

After the packer is planted, hydraulic fracturing is carried out with a hydrocarbon fluid, for example, oil located, including in the tubing. The fact of hydraulic fracturing is determined by an abrupt decrease in pressure. Behind the fracturing fluid, a hydrocarbon fluid, a hydrocarbon fluid with hydrophobized propant is successively pumped. The total volume of fluid for hydraulic fracturing and transportation of proppant for fixing hydraulic fractures is determined by calculation.

Information sources

1. Muravyov I.M. and other Development and operation of oil and gas fields, - Moscow, Nedra, 1970, p. 102-103;

2. RF patent No. 2113590 (prototype).

Claims (1)

The method of hydraulic fracturing, including fracturing a hydrocarbon fluid that is close or identical in properties to the hydrocarbon fluid extracted from the reservoir, and subsequent transportation to the proppant fluid in the form of particles of bentonite hydrophobized clay with a fractional composition of 0.1 ÷ 30 μm in an amount of 2-5% of the weight of the hydrocarbon base of the liquid in the propant transportation fluid containing, wt.%: Hydrocarbon fluid  15-30 Surface-active substance - Cationic or anionic surfactants  0.05-0.1 Water  Rest