RU2494243C1 - Well operation intensification method - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method involves perforation made by means of a drilling or milling method, performance of hydraculic fracturing through the formed perforation holes and development of a well. Perforation density is accepted equal to not more than 10 holes per running metre of the perforation interval; hydraulic fracturing is performed in series in the formations separated with a waterproof bridge with thickness of not less than 7 m. Hydraulic fracturing of each formation is performed in a partial load mode with low fracturing liquid flow rate of not more than 2.0 m³/min, with reduced liquid flow rate at replacement of the well volume with crosslinked gel to the value of not more than 1.0 m³/min, decreased proppant concentration of not more than 1100 kg/m³ and the wellhead pressure of not more than 22 MPa.

EFFECT: improving intensification efficiency of a well developing a multi-zone reservoir.

Description

The invention relates to the oil industry and may find application in stimulating well operations.

A known method of hydraulic fracturing, including opening the formation with a vertical or directionally directed well with the placement in it, in a predetermined interval of the formation, of a sandblasting perforator, with pumping of working fluid through the jet nozzles of a sandblasting perforator to form gaps (cavities) in the reservoir, followed by fracturing of the formation through the formed cracks (RF Patent No. 2311528, publ. 11/27/2007).

The disadvantages of this method are:

1. Limiting the length of the perforation interval, since the duration of the process leads to abrasive destruction of the hydraulic nozzles during the perforation, due to the presence of sand in the composition of the working fluid opening (a mixture of sand with water), which does not provide further opening of the casing string and reservoir .

2. The deposition of sand in the wellbore during the sandblasting perforation for the direction of hydraulic fracturing (hydraulic fracturing), which requires additional measures for flushing the well before hydraulic fracturing.

3. Carrying out hydraulic fracturing through jet nozzles of a sandblasting puncher, which create additional hydraulic resistances by injection of fracturing fluid and sand carrier.

4. The proppant particle size limitation and proppant concentration limitation, since jet nozzles have limitations in diameter and throughput.

5. The ability to rotate the sandblasting perforator relative to the azimuth during perforation in the wellbore, thereby changing the position of the subsequent formation of the gap in time.

6. Additional sandblasting perforation in a predetermined early perforated interval of the reservoir, if the perforation was cumulative, this combination will reduce the strength of the production string, and it is also possible to break the reservoir along the perforations depending on the number of holes per meter of the reservoir.

Closest to the proposed invention in technical essence is a method of conducting directed hydraulic fracturing, which includes opening the formation with a vertical or directional well, perforating in a given interval of the producing formation with pumping the working fluid to form gaps in the formation and subsequent fracturing of the formation through the formed gaps. In this case, perforation in a vertical or directional well is carried out in a previously unperforated interval of the reservoir by means of a hydromechanical slotted perforator, with the help of which azimuthally oriented cracks are formed. After completion of the formation of the slit, the hydromechanical slotted punch is removed from the well, and then tubing with a packer is lowered. A directed hydraulic fracturing is carried out at a given interval of the productive formation through the formed gap. After that, the tubing with the packer is lifted and the tubing with the flushing tool is lowered, with the help of which the current bottom hole is flushed. Next, an insulating sand bridge is installed, with the help of which the formed gap crack is isolated. Then the tubing with the flushing tool is lifted and the tubing with a hydromechanical slotted punch, azimuthally oriented in the well, is lowered. The next gap is formed, through which the hydraulic fracturing operation is repeated for each newly formed gap. The resulting fracture cracks from the following fracturing operations are isolated with a sand bridge. Then the tubing with the flushing tool is lowered and the artificial bottom hole is flushed to the current bottom hole. In the presence of a large thickness of the reservoir, the formation of cracks, and consequently, rupture cracks, is staggered 90 ° relative to each other, or gaps are formed in pairs, in which the cracks are 180 ° relative to each other, and pairs are formed in a checkerboard pattern each other at 90 °. Each newly formed gap through which the hydraulic fracturing operation is repeated is isolated by a sand bridge (RF Patent No. 2452854, publ. 10.06.2012 - prototype).

The disadvantage of the prototype is that the method is successfully and effectively applicable only to terrigenous reservoirs of the Devonian. In other conditions and in the conditions of multilayer deposits, when it is necessary to intensify oil production from different reservoirs at different depths in one well, the method is ineffective or even leads to the opposite effect, which is expressed in watering the well.

The proposed invention solves the problem of stimulation of the well, which revealed the multilayer reservoir.

The problem is solved in that in the method of intensifying the operation of the well, including perforation using a drilling or milling method, hydraulic fracturing through formed perforations and well development, according to the invention, the perforation density is assigned no more than 10 holes per linear meter of the perforation interval, hydraulic fracturing is carried out in the formation, separated by an impermeable bridge with a thickness of at least 7 m, hydraulic fracturing is carried out in a gentle mode with a low flow rate of the fracture fluid of not more than 2.0 m ³ / min., with a flow rate of fluid when replacing the volume of the well with a cross-linked gel no more than 1.0 m ³ / min., low proppant concentration no more than 1100 kg / m ³ and pressure at the wellhead no more than 22 MPa.

SUMMARY OF THE INVENTION

In the conditions of multi-layer deposits, when it is necessary to intensify oil production from different reservoirs at different depths in one well, the known methods of hydraulic fracturing are ineffective or even lead to the opposite effect, which is expressed in watering the well. The proposed invention solves the problem of stimulation of the well, which revealed the multilayer reservoir. The problem is solved as follows.

To intensify the operation of the well, a well is selected that has opened productive formations separated by an impermeable bridge at least 7 m thick.In the intervals of productive formations, perforation with a perforation density of not more than 10 holes per linear meter of the perforation interval is performed using a drilling or milling method. Hydraulic fracturing is carried out sequentially in productive formations. Hydraulic fracturing of each formation is carried out in a gentle manner with a low flow rate of fracture fluid of the order of 1.8-2.0 m ³ / min., With a reduced fluid flow rate when replacing the well volume with a cross-linked gel to a value of not more than 1.0 m ³ / min., reduced proppant concentration of about 900-1100 kg / m ³ and reduced pressure at the wellhead to a value of about 15-22 MPa.

For the implementation of hydraulic fracturing, among others, the following components can be used:

1. gelling agent:

- GPG-3 TU 2499-072-17197708-2003 manufacturer of ZAO Petrokhim, Russia;

- WG-40DS manufacturer "Economy Polymers & Chemicals", USA;

- Jaguar 415 producer of "New energy resources", USA;

2. clay stabilizer:

- potassium chloride "small" GOST 4568-95, Russia;

- WCS-100 manufacturer "Economy Polymers & Chemicals", USA;

- Stabilizer 10 manufacturer "New energy resources", USA;

3. demulsifier:

- WNE-135 manufacturer "Economy Polymers & Chemicals", USA;

- Sulfactant non-2 manufacturer "New energy resources", USA;

- DSCo DM-1 manufacturer "Chevron Phillips Chemical Company LP" USA;

4. activator of destruction:

- PAV-RD TU 2499-072-17197708-2003 manufacturer of ZAO Petrokhim, Russia;

- EB-A manufacturer "Economy Polymers & Chemicals", USA;

- AP-Activator manufacturer "New energy resources", USA;

5. destructor:

- HV destructor TU 2499-074-17197708-2003 manufacturer ZAO Petrokhim, Russia;

- WGB-1 manufacturer "Economy Polymers & Chemicals", USA;

- Breaker P manufacturer "New energy resources", USA;

6. stapler:

- Borate stapler BS-1 TU 2499-069-17197708-2003 manufacturer ZAO Petrokhim, Russia;

- WGXL-10.1 manufacturer "Economy Polymers & Chemicals", USA;

- Crosslinker manufacturer "New energy resources", USA.

Water with a gellant dissolved in it is called a gel. A gel with a crosslinker is called a crosslinked gel. A crosslinked gel with a clay stabilizer, a demulsifier, a gel degradation regulator and a gel destructor is called a fracturing fluid. The proppant rupture fluid is called a proppant gel mixture.

Initially, based on the available geological data, they draw up a hydraulic fracturing plan, which is specified during the test injection and draw up an updated plan.

The well is equipped with a tubing string with a packer above the interval of the reservoir. All work is carried out with the packer set.

At the end of the delivery and placement of equipment on the territory of the well, a discharge line is connected with wellhead fittings and external sensors are connected, a set of process water is made for a test injection. In the process of water collection, technical water is sampled from each tanker and analyzed for the content of mechanical impurities, the content of free hydrogen ions, and the temperature is determined. The content of free hydrogen ions, pH should be in the range of 6.5-8.5, temperature - in the range of 10-40 ° C.

At the end of the set of water, test preparation of the fracturing fluid is carried out.

- test for dissolving and stitching. A gelling agent is added to the water. Mixing for 15-20 minutes is carried out at a Warell type mixing plant, then the viscosity of the resulting suspension is measured on a Fann-35 measuring device (at a temperature of 23 ° C, the viscosity should be 21 cP +/- 2 cP). With a satisfactory result, a gel crosslinker is added to the resulting suspension with constant stirring. Stitching time, i.e. structure formation of the composition should be no more than 10 s.

With a satisfactory result, the gelling agent is loaded. At the end of the load, the calculated amount of the reagent produces technological exposure for 15-20 minutes. for blooming, i.e. to dissolve the gelling agent with constant stirring using the centrifugal pump of the MS-60 or MT-60 blender according to the blender-mixing tank system. After the mixing time has elapsed, a sample of the obtained gel is again taken, the temperature and viscosity of the selected sample are measured, and again checked for crosslinking. With satisfactory results, the remaining reagents are added: a gel destruction regulator, a clay stabilizer. After adding and bringing to a homogeneous state by stirring for 25-30 minutes start and warm up the discharge pumps.

Perform a test download. In a test injection, the first step is to replace the well volume with a fracture fluid. Replacement is carried out by injection of a fracturing fluid with a reduced flow rate of not more than 1.0 m ³ / min. into the wellbore. As it is injected, a gel crosslinker and a crosslinked gel destructor are fed into the flow to form a fracture fluid. The volume is changed based on the calculation of the volume of the tubing string to the packer equipment + sub-packer zone to the roof of the perforation interval, i.e. total from 5.5 to 9.5 m ³ depending on the downhole equipment used and the design of the well. Having downloaded the required volume of the fracturing fluid, the injection is stopped. A pressure drop is recorded for 10 minutes. to assess the change in friction losses and the reaction of the reservoirs to pumping fluid at a low speed. Replacing the volume is necessary to eliminate errors in processing the results of the test injection, because when initiating a fracture in water (with a dynamic viscosity of less than 2-3 cP), the geometry of the resulting fracture is not characteristic, which is associated with a high percentage of filtering into the reservoir and large friction losses when moving along the wellbore and fracture in the reservoir.

At the end of the recording of the pressure drop, the injection of the fracturing fluid is resumed already at a flow rate of hydraulic fracture of the order of 1.8-2.0 m ³ / min. and reduced pressure at the wellhead to a value of the order of 15-22 MPa.

At the same time, the “pillow” is pumped in first, i.e. the volume of liquid is from 3 to 6 m ³ . A cushion is the volume of fluid required for the pump units to flow and re-open a crack in the formation. Then, a test pack of proppant in a volume of 500-1000 kg with a concentration of 30 to 200 kg / m ³ for the MT-60 blender and 120-200 kg / m ³ for the MS-60 blender, where the initial concentration is associated with limitations on the operation of the equipment used. The volume of injected proppant can be varied up to 1 ton, which depends on the effective thickness of the fracturing object. With a thickness of up to 4 m, 500 kg is enough, with a thickness of 4 m or more, it is advisable to use a larger volume. The permeability of the formation does not play a big difference, since it is primarily important to distribute the incoming proppant volume of the test pack as much as possible over the entire height of the initiated fracture, or rather, the perforation interval of the fracturing object. The volume of injected proppant-gel mixture may vary depending on the volume of the test pack and the concentration of proppant feed. Subject to design data, for example, the proppant volume is 500 kg, the concentration is from 30 to 200 kg / m ³ , the mixture volume should be 4.4 m ³ .

After pumping a test pack of proppant with a concentration of up to 200 kg / m ³ and bringing it to the perforation interval, the initial wellhead pressure is noted and then the nature of its change during the passage of the pack through the perforation interval and its movement along the crack is recorded. The ideal state of hydrodynamic communication with the formation does not give rise to wellhead pressure and when it moves along the formation, it also does not change. The increase in pressure during the passage of the test pack through the perforation interval to 1 MPa is a sign of a satisfactory connection and allows the fracturing process to be carried out without changing the basic plan. The presence of a pressure increase from 1 to 2.5 MPa is a sign of the possibility of complications at proppant concentrations of more than 350-400 kg / m ³ , that is, a significant increase in wellhead pressure up to a premature "STOP" - termination of the injectivity of the formation. The presence of pressure growth from 2.5 or more MPa is a sign of premature STOP already at minimum proppant concentrations of 200 or more kg / m ³ .

If the wellhead pressure increases when the proppant pack passes through the perforation interval by 1 to 2.5 MPa during the main hydraulic fracturing process, the volume of injected proppant of small and medium fractions is increased (no more than 20/40, 16/30 and 16/20 mesh ) at minimum concentrations up to 200 kg / m ³ up to 900-1100 kg per stage, against the standard volume to be laid during design up to 500 kg. At the same time, the resulting erosion effect due to the destruction of the rock on the walls of the crack allows to increase the radius of sinuosity of the crack in the bottom of the formation and to clean the perforations. The effectiveness of this measure is estimated by decreasing wellhead pressure as this pack of proppant passes through the perforation zone and when pressure decreases by 1 or more MPa, it can be concluded that the hydraulic connection with the formation is improved. In the absence of signs of restoration of communication with the formation, the proppant supply concentration in the following stages is promptly reduced, being limited to maximum values of 350-400 kg / m ³ .

At the end of the injection of a trial pack of proppant, it is sold into the reservoir. At the same time, the first 1.5-1.6 m ^{3 of the} squeeze is produced by a fracturing fluid, which is necessary to prevent smearing of part of the proppant along the walls of the tubing string and casing string by mixing fluids with different viscosities. Then it is possible to stop the stapler and destructor and the remaining volume of selling is done on a gel in the total volume “tubing string + sub-packer zone to the roof perforation interval + 3 m ³ ” to push the proppant pack into the depth of the crack to determine the degree of friction pressure loss in the bottomhole formation zone. After the injection, the pumping units are stopped, the pressure drop is recorded for 1 hour. Moreover, in real time, recording and processing the intensity of wellhead pressure decrease is performed. Based on the Meyer software package, the obtained data are processed, where, according to the dependencies of the linear Horner and Nolti-Smith equations, the following data are obtained: fracture fluid working efficiency, net pressure value, stress gradient in the fracturing reservoir, time and pressure of fracture closure, pore pressure reservoir, hydraulic pressure loss in the interval of perforation and the bottom of the reservoir. Based on the obtained data, the design data are adapted, such as stress gradients along the section of the formations above and below the hydraulic fracturing object, the values of fluid filtration and instantaneous leaks, the value of Young's modulus to the received test injection processing data. The corrected data is downloaded to a computer to re-calculate the three-dimensional hydraulic fracturing model and draw up an updated modified fracturing plan (concentration and amount of proppant injection, pillow volume, injection speed and the order of concentration change when the destructor is fed) during the main fracturing process.

Based on the calculations made, a set of the required volume of process water is prepared and a fracturing fluid is prepared with testing. With satisfactory test results, hydraulic fracturing is started.

The hydraulic fracturing process is carried out in accordance with a detailed revised plan, where the volume of the final sale is defined as the sum of the volume of the tubing string and sub-packer zone to the roof of the perforation interval.

The destructor is introduced into the flow of injected fluid using a dry chemical feed pump in accordance with the injection rate. The dry chemical feed pump includes a screw for the dosed supply of a dry destructor. The dosage management of the dry destructor feed is carried out in two ways. In the case of using the MT-60 blender as a mixing unit from the control panel manually, in the case of using the MS-60 blender as a mixing unit in automatic mode by changing the parameters in the Accufrac blender control program. In both cases, the planned change in the concentration of the feed of the destructor is the same.

When the first portion of the proppant-gel mixture is pumped with a proppant concentration of up to 300 kg / m ^{3, the} dosage of the destructor is carried out according to the concentration, which ensures the complete process of gel decomposition and crack closure time of at least 12 hours. When the second portion of the proppant-gel mixture is injected (proppant concentration is greater than 300 kg / m ³ ), the dosage of the destructor is carried out according to the concentration that ensures the process of complete decomposition of the gel and the crack closing time of no more than 4 hours.

After the proppant-gel mixture is sold, the pumping units are stopped and a pressure drop is recorded for 15 minutes to obtain information about the quality of the hydraulic fracturing process, the pressure drop intensity, the presence of a residual connection with the formation (water hammer), and the absence of an overselling effect. After that, the wellhead is closed, the equipment is dismantled, and the well is left to wait for the pressure drop and gel destruction.

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 bleeding is done after 4 hours as follows: at a pressure of more than 4.0 MPa on the wellhead gauge, bleeding is performed with a flow rate of not more than 30 l / min to atmospheric pressure, at a pressure of less than 4.0 MPa on the wellhead gauge made by the full opening of the wellhead valve.

Further, the wellhead is depressurized, the packer is stalled and the equipment is hoisted.

Depending on the development needs, the second reservoir in this well is subjected to hydraulic fracturing immediately after the first or after some time during which the well is operated.

Concrete example

Intensify the operation of oil producing wells.

The object of intensification: the Sbr3 formation in the interval 1244-1247 m is separated from the underlying aquifer by a clay bridge 7 m thick.

Object lithology: sandstones (absolute permeability 1300 mD, phase permeability 563.4 mD).

Well and running equipment design: production string with a diameter of 168 mm is tight.

Perforation before hydraulic fracturing is carried out by the PGSP-112 drilling system (on cable) in the range of 1244-1247 m perforation density of 10 holes per linear m of the interval.

The tubing is lowered, the face is poured with a sand bridge to a depth of 1250.7 m.

The packer is lowered on a tubing string with a diameter of 89 mm to a depth of 1234 m and the packer is planted.

Objects opened by perforation, not participating in hydraulic fracturing: none.

Perform a test download. The initial injection rate of the fracturing facility is Q-240 m ³ / day., The initial pressure is Pnach = 10 MPa, the final pressure is Pcon = 13 MPa. The quality of communication with the formation is determined by injecting 5.2 m ^{3 of} technical fluid with a density of 1.05 g / cm ³ without preliminary saturation of the bottomhole zone.

Fracture design data is assigned: gel volume 51 m ³ based on the Econotec reagent kit (WG 40 LDS liquid-based), proppant amount 7 tn (20 / 40-1 tn, 16 / 30-3 tn, 12 / 18-3 t). The proposed fluid flow rate is not more than 1.8 m ³ / min, expected wellhead pressures Rnach = 18.5 MPa, Rrab = 13.7 MPa. The estimated crack length created is 59.35 m, the crack length is fixed at 59.17 m, the height of the crack is 16.8 m, and fixed is 3.4 m. The net fracture pressure is 5.2 MPa. The maximum crack width is 12.1 mm at the perforation interval, the residual width after depressurization is 3.2 mm.

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 20 m ³ based on the WG 40 LDS Econotec liquid gelling agent with a load of 7.5 l / m ³ . 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.

The tubing is pumped into the string and the tubing string is replaced with a fracture fluid of 5.49 m ³ at a rate of 1 m ³ / min. at a final pressure of 17 MPa. A test injection is made with recording the pressure drop and processing the obtained data on the pressure drop - in the volume of 18 m ^{3 of} fracturing fluid with the addition of 500 kg of proppant fraction 20/40. The test pack went through the perforation interval with a pressure increase of 1.5 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 data of the test injection processing,

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 drawn up plan with the proppant concentration in stages: 120 kg / m ³ , 200 kg / m ³ , 400 kg / m ³ , 600 kg / m ³ , 800 kg / m ³ , 1000 kg / m ³ and pressure at the wellhead 20 MPa, where the volume of the final sale is defined as the sum of the volume of the tubing string and the sub-packer zone to the roof of the perforation interval minus the volume of the estimated undersupply. The maximum flow rate in the main process is 1.8 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: crack length created (one wing) 68.5 m, fixed - 67.8 m, crack height created 12.8 m, fixed - 3.4 m, signs of breakthrough in there is no underlying waterlogged formation starting at a depth of 1255 (8 meters lower). The width of the fracture after relieving pressure is 3.98 mm, the proppant concentration in the interval of the productive part of the formation is 5.16 kg / m ² against the design 4.2 kg / m ² .

The well was put into operation 4 days after the completion of hydraulic fracturing with an increase in fluid flow rate of more than 3 times (without an increase in water cut), the productivity coefficient increased by 2.3 times.

Thus, the proposed method allows for hydraulic fracturing in a gentle mode, with the creation of a highly conductive crack in the Bobrikov deposits with high permeability, eliminating the risks of breakthrough of the crack in the underlying flooded reservoir. The application of the proposed method will intensify the work of deposits with Bobrikov deposits.

The application of the proposed method will solve the problem of stimulation of the well, which revealed the multilayer reservoir.

Claims (1)

A method of intensifying well operation, including perforation using a drilling or milling method, hydraulic fracturing through formed perforation holes and well development, characterized in that the perforation density is assigned no more than 10 holes per linear meter of the perforation interval, hydraulic fracturing is carried out in a formation separated by an impermeable bridge with a thickness of not less than 7 m, hydraulic fracturing is carried out in a gentle mode with a low flow rate of the fracture fluid of not more than 2.0 m ³ / min, with a fluid flow rate when replacing the volume of wells ina for a crosslinked gel is not more than 1.0 m ³ / min, a reduced proppant concentration is not more than 1100 kg / m and the pressure at the wellhead is not more than 22 MPa.