CN110284861A - A method of intrinsic fracture heavy crude reservoir is exploited using Degradable temporary blocking agent auxiliary SAGD - Google Patents

Abstract

The present invention discloses a kind of method using Degradable temporary blocking agent auxiliary SAGD exploitation intrinsic fracture heavy crude reservoir, the following steps are included: injection high temperature resistant Degradable temporary blocking agent, its diverting agent enters the region of intrinsic fracture or high permeability zone connection, gel is generated in intrinsic fracture, so that fracture plays plugging action；After injecting high temperature resistant Degradable temporary blocking agent, pressure testing is carried out, judges whether intrinsic fracture or high permeability zone have successfully blocked by the comparison of observation injection flow and injection pressure；After blocking successfully, then dilatation operation is implemented to the entire horizontal segment of injection-production well；After the completion of dilatation operation, high-temperature steam is injected in injection-production well and carries out normal thermal cycles, forms thermal communication between injection-production well.Degradable temporary blocking agent is applied to the intrinsic fracture in blocking SAGD application oil reservoir by the present invention, and bottomhole injection pressure to be achieved needed for realizing rapidly pre-warming shortens preheating cycle, reduces steam injection dosage and cost；Improve the thermal efficiency and economic benefit of thickened oil recovery.

Description

A method of using degradable temporary plugging agent to assist SAGD to exploit natural fractured heavy oil reservoirs method

technical field

The invention relates to a method for utilizing a degradable temporary plugging agent to assist SAGD in exploiting natural fracture heavy oil reservoirs, and belongs to the technical field of petroleum engineering oil and gas field development.

Background technique

Steam-assisted gravity drainage (SAGD) is a cutting-edge technology for the development of heavy oil reservoirs. The application of SAGD technology is mainly carried out on two vertically parallel horizontal wells, in which the upper horizontal well is used as an injection well, and the lower horizontal well is used as a production well (Fig. 1). The first stage of the application of SAGD technology is the cycle preheating stage, that is, to establish thermal communication between the oil layer between the injection well and the production well through different heating methods, so that the injected steam can continuously flow into the oil layer, and the heated crude oil and condensed water can be continuously heated. flow to production wells, so as to realize the continuous development of the steam chamber, so as to achieve efficient heavy oil recovery

In order to establish thermal communication between injection and production wells of SAGD, it is usually realized by circulating steam injection in injection wells and production wells (Fig. 2). However, field experience shows that it takes a long time (more than 150 to 200 days) to form thermal communication between injection and production wells through conventional steam circulation. This not only increases the time cost, but also consumes a large amount of steam, which reduces the benefits of using the SAGD technology.

In order to shorten the time required for the connection of injection and production wells, save the steam consumption in the thermal cycle stage, and improve the thermal efficiency and economic benefits of heavy oil production, the oil squeeze expansion reservoir reconstruction technology can be used in the near wellbore area under the condition close to the fracture pressure of the oil layer. Downward injection of hot water or light oil or a mixture of these two fluids increases the pressure difference between injection pressure and formation pressure in the near wellbore area by controlling the wellhead pressure, and improves the near wellbore area by changing the rock properties of the formation well zone permeability and porosity purposes. However, if this method is applied to formations with natural fractures, the injected fluid will easily leak into the formation along the natural fractures. Moreover, it is possible to form the main channel between injection and production wells through natural fractures, so that most of the injected steam will be lost through the main channel, resulting in uneven preheating and fluid communication, and under the conditions of initial hot water injection or low steam rate, It is impossible to achieve the required injection pressure at the bottom of the well, and it is difficult to achieve the purpose of near-well expansion and rapid preheating (Fig. 3).

Contents of the invention

The present invention mainly overcomes the deficiencies in the prior art. In order to improve the start-up and commissioning efficiency of SAGD wells in natural fractured reservoirs, a method for using degradable temporary plugging agents to assist SAGD in natural fractured heavy oil reservoirs is proposed.

The technical solution provided by the present invention to solve the above technical problems is: a method for utilizing a degradable temporary plugging agent to assist SAGD in mining natural fractured heavy oil reservoirs, comprising the following steps:

Step S10, injecting a high-temperature-resistant degradable temporary plugging agent in the production well or the injection well, or in the production well and the injection well at the same time, and the temporary plugging agent enters the connected area of the natural fracture or the high-permeability zone, and generates gel in the natural fracture, to seal the cracks;

Step S20, after injecting the high-temperature-resistant degradable temporary plugging agent, conduct a pressure test, and judge whether the natural fracture or the high-permeability zone has been successfully blocked by observing the comparison between the injection flow rate and the injection pressure; if the plugging is not successful, continue to inject the resistant High temperature degradable temporary plugging agent; if the plugging is successful, proceed to the next step;

Step S30, then injecting hot water or light oil or a mixture of these two fluids into the entire horizontal section of the injection-production well to squeeze liquid and expand capacity;

Step S40, after the expansion operation is completed, high-temperature steam is injected into the injection-production well to carry out a conventional thermal cycle to form thermal communication between the injection-production wells;

When the wellbore and formation temperature exceeds 150°C, the high-temperature-resistant and degradable temporary plugging agent remaining in the near-wellbore zone and fractures will degrade and return to the ground with the circulating fluid. The degraded temporary plugging agent will not cause damage to the formation.

A further technical solution is that in the step S10, a high-temperature-resistant degradable temporary plugging agent is injected into the production well and the injection well at the same time.

A further technical solution is that in the step S10, the injection volume of the high-temperature-resistant degradable temporary plugging agent is about 1-20 m ³ , and the injection temperature does not exceed 100°C.

A further technical solution is that in the step S20, when the injection pressure increases and the injection flow rate decreases significantly, it is judged that the plugging is successful.

A further technical solution is that in the step S30, the specific process of circulating hot water injection or light oil squeeze liquid expansion operation is: injecting hot water or light oil or the two fluids into the formation through the injection string of the injection well Then adjust the injection pressure or injection flow rate, so that the injected steam accumulates in the near-wellbore zone and causes the near-wellbore zone pressure to quickly approach the formation fracture pressure, forming micro-fractures in the near-wellbore zone, thereby improving the permeability and porosity of the near-wellbore zone Spend.

A further technical solution is that in the step S30, the expansion effect of the formation under the design conditions is obtained by detecting changes in the downhole pressure and injection rate in the horizontal section during the expansion process.

Beneficial effects of the present invention: the present invention applies the degradable temporary plugging agent to plug the natural fractures in the SAGD application oil layer, realizes the bottom hole injection pressure required for rapid preheating, shortens the preheating period, reduces the amount and cost of steam injection; finally improves Thermal efficiency and economic benefits of heavy oil recovery.

Description of drawings

Fig. 1 is a schematic diagram of a SAGD well group in an oil layer with natural fractures;

Fig. 2 is a schematic diagram of the early stage of establishing heat communication through the steam injection cycle;

Fig. 3 is a schematic diagram of the late stage of establishing thermal communication through the steam injection cycle;

Fig. 4 is the synoptic diagram of injecting temporary plugging agent in production well and injection well simultaneously in embodiment 1;

FIG. 5 is a schematic diagram of establishing thermal communication in Embodiment 1. FIG.

Detailed ways

The present invention will be further described below in conjunction with the embodiments and the accompanying drawings.

Example 1

A kind of method that utilizes degradable temporary plugging agent of the present invention to assist SAGD exploitation natural fracture heavy oil reservoir, comprises the following steps:

Step S10, as shown in Figure 1, inject a certain amount of high-temperature-resistant and degradable temporary plugging agent into the production well and the injection well at the same time, and the temporary plugging agent preferentially enters the natural fractures with better permeability or the connected areas of high-permeability zones. A gel with high stress strength is produced in the natural fracture, so that the subsequent injection of hot water or light oil or the mixture of these two fluids cannot enter the fracture or high permeability area, thereby sealing the fracture;

The injection volume of the above-mentioned temporary plugging agent can be determined according to the length of the horizontal well and the development degree of natural fractures, generally about 1-20m ³ , and the injection temperature should not exceed 100°C;

Step S20, after injecting the high-temperature-resistant degradable temporary plugging agent, conduct a pressure test, and judge whether the natural fracture or the high-permeability zone has been successfully blocked by observing the comparison between the injection flow rate and the injection pressure;

Among them, when it is observed that the injection pressure rises and the injection flow rate drops significantly, it can be judged that the plugging has been successful;

If the plugging is not successful, continue to inject the high-temperature-resistant degradable temporary plugging agent, and then make a judgment until the plugging is successful and proceed to the next step;

Step S30, then injecting hot water or light oil or a mixture of these two fluids into the entire horizontal section of the injection-production well to squeeze liquid and expand capacity, that is, inject hot water or solvent or solvent into the formation through the injection string of the injection-production well. Liquid mixture, by adjusting the injection pressure or injection flow rate, the injected fluid accumulates in the near-wellbore zone and causes the near-wellbore zone pressure to quickly reach the expansion pressure, forming micro-fractures in the near-wellbore zone, thereby improving the permeability and permeability of the near-wellbore zone. Porosity;

In the above expansion process, the expansion effect of the formation under the design conditions can be obtained by detecting the change of downhole pressure and injection rate in the horizontal section;

Step S40, after the capacity expansion operation is completed, as shown in Figure 5, high-temperature steam is injected into the injection-production well to carry out a conventional thermal cycle to form thermal communication between the injection-production wells;

When the wellbore and formation temperature exceeds 150°C, the high-temperature-resistant degradable temporary plugging agent remaining in the near-wellbore zone and fractures will degrade and return to the ground with the circulating fluid. The degradation temperature and action time of the high-temperature-resistant degradable temporary plugging agent can be The formula is designed according to the operating parameters of formation expansion, and the degraded temporary plugging agent will not cause damage to the formation.

The above-mentioned embodiment is for the pretreatment of the SAGD well group with natural fractures, plugging the natural fractures, reducing the risk of local connection of injection and production wells for the high-pressure expansion operation of the SAGD well group, creating conditions for improving the uniform preheating of the horizontal section, and realizing rapid preheating at the same time , shorten the preheating cycle, reduce the amount of steam injection and cost.

The above description does not limit the present invention in any form. Although the present invention has been disclosed by the above-mentioned embodiments, it is not intended to limit the present invention. When the technical content disclosed above can be used to make some changes or be modified into equivalent embodiments with equivalent changes, but if they do not deviate from the content of the technical solution of the present invention, any simple modifications made to the above embodiments according to the technical essence of the present invention, equivalent Changes and modifications all still belong to the scope of the technical solution of the present invention.

Claims (6)

1. a kind of method using Degradable temporary blocking agent auxiliary SAGD exploitation intrinsic fracture heavy crude reservoir, which is characterized in that including Following steps:

Step S10, in producing well perhaps injection well or simultaneously to inject high temperature resistant Degradable temporary in producing well and injection well stifled Agent, diverting agent enters the region of intrinsic fracture or high permeability zone connection, gel is generated in intrinsic fracture, so that fracture rises To plugging action；

Step S20, after injecting high temperature resistant Degradable temporary blocking agent, pressure testing is carried out, passes through observation injection flow and injection pressure Comparison judge whether intrinsic fracture or high permeability zone have successfully blocked；Continuing injection high temperature resistant if blocking not successfully can Degradation diverting agent；Next step is carried out if blocking successfully；

Step S30, implement the mixing of injection hot water or light oil or both fluids to the entire horizontal segment of injection-production well again Object squeezes liquid dilatation operation；

Step S40, after the completion of dilatation operation, high-temperature steam is injected in injection-production well and carries out normal thermal cycles, is formed between injection-production well Thermal communication；

After pit shaft and formation temperature are more than 150 DEG C, the high temperature resistant Degradable temporary blocking agent remained near wellbore zone and crack is logical Degradation is crossed, returns to ground with circulation of fluid, the diverting agent after degradation will not generate injury to stratum.

2. a kind of side using Degradable temporary blocking agent auxiliary SAGD exploitation intrinsic fracture heavy crude reservoir according to claim 1 Method, which is characterized in that inject high temperature resistant Degradable temporary blocking agent in the step S10 in producing well and injection well simultaneously.

3. a kind of utilization Degradable temporary blocking agent auxiliary SAGD according to claim 1 or 2 exploits intrinsic fracture heavy crude reservoir Method, which is characterized in that the injection rate of high temperature resistant Degradable temporary blocking agent is in 1-20m in the step S10³Left and right, injection pressure Power is no more than 90% formation fracture pressure, and injection temperature is no more than 100 DEG C.

4. a kind of utilization Degradable temporary blocking agent auxiliary SAGD according to claim 1 or 2 exploits intrinsic fracture heavy crude reservoir Method, which is characterized in that in the step S20 when injection pressure rises and injects flow velocity and be remarkably decreased, then judge to block Success.

5. a kind of side using Degradable temporary blocking agent auxiliary SAGD exploitation intrinsic fracture heavy crude reservoir according to claim 1 Method, which is characterized in that hot-water flooding or light oil squeeze the detailed process of liquid dilatation operation in the step S30 are as follows: are adopted by note The injection string of well injects the mixture of hot water or light oil or both fluids to stratum, then regulates and controls injection pressure Or injection flow velocity, make to inject the dilatation pressure that fluid accumulates near wellbore zone and near wellbore zone pressure is caused to be rapidly achieved stratum Power changes the mechanical properties of rock near wellbore zone region, so as to improve the permeability and porosity of near wellbore zone.

6. a kind of side using Degradable temporary blocking agent auxiliary SAGD exploitation intrinsic fracture heavy crude reservoir according to claim 5 Method, which is characterized in that pass through the inspection to the variation of horizontal segment down-hole pressure and charge velocity in dilation process in the step S30 It surveys, obtains the stratum capacity enlargement effect under design condition.