CN104655808B - A kind of Fracture with low permeability oil reservoir imbibition oil recovery experimental technique - Google Patents

Abstract

The invention relates to an experimental method for oil recovery by imbibition in a low-permeability fractured oil reservoir. It mainly solves the problem that the existing dynamic imbibition experimental research method is difficult to accurately reflect the influence of various factors in the experiment on the dynamic imbibition oil recovery process. It is characterized in that it includes the following steps: (1) mould; (2) batching; (3) sand mixing; (4) initial mold loading and pressurization; (5) spreading sulfuric acid paper interlayer; (6) secondary mold loading (7) heating; (8) coring; (9) vacuum saturated water; (10) saturated formation crude oil; (11) dynamic imbibition experiment: take out the rock core, remove the plastic film in the middle of the rock core and the winding Tape, and then re-seal the arc-shaped outer surface and two end faces of the core, inject water and oil displacement agent through the core along the fracture, and use this method to simulate the process of imbibition oil production in fractured reservoirs. The experimental method for the imbibition oil recovery process of the low-permeability fractured reservoir can ensure that the oil saturation of the matrix core is not affected by fractures, simplifies the operation steps of the existing experimental method, and improves the accuracy of the dynamic imbibition experiment.

Description

An experimental method for imbibition recovery in low-permeability fractured reservoirs

Technical field:

The invention relates to the technical field of oil reservoir development, in particular to an experimental method for imbibition oil recovery in low-permeability fractured oil reservoirs for research on dynamic imbibition oil recovery effects and influencing factors of low-permeability fractured oil reservoirs.

Background technique:

In the development of low-permeability fractured reservoirs, the problem of low water flooding recovery caused by serious water flooding of oil wells and rapid rise of water cut often occurs. The current laboratory research and field tests have shown that the cross-seepage flow between the injected water and the matrix rock of the reservoir can be realized through the water injection huff and puff oil recovery technology, thereby reducing the oil saturation of the matrix core and increasing the degree of crude oil recovery. With the deepening understanding of low-permeability fractured reservoirs by oilfield scientific and technological workers, some people have proposed to fine-tune the parameters of water injection huff and puff recovery technology to enhance the effect of dynamic imbibition between fractures and matrix. Since field practice requires relevant experimental research to provide a theoretical basis, it is very necessary to carry out laboratory dynamic imbibition oil recovery experimental research to optimize various parameters. At present, the main steps of dynamic imbibition oil recovery experiment research are as follows: first, saturate the core with formation water and formation crude oil, then cut the core to create fractures or use a triaxial rock mechanics instrument to apply external force to create fractures, and finally carry out dynamic imbibition experiments. However, the above-mentioned fracture-making methods all have technical problems such as troublesome operation, difficulty in controlling the fracture shape and geometric size, and the influence of the oil saturation of the core matrix during the fracture-making process, and cannot guarantee that the fracture shape and position of each batch of fracture-making cores are the same. As a result, the experimental research cannot accurately reflect the influence of various factors on the dynamic imbibition recovery process.

Invention content:

The present invention aims to overcome the problem that the existing dynamic imbibition experimental research method in the background technology is difficult to accurately reflect the influence of various factors in the experiment on the dynamic imbibition recovery process, and provides a low-permeability fractured reservoir imbibition recovery process experiment method. The experimental method for the imbibition oil recovery process of the low-permeability fractured reservoir can ensure that the oil saturation of the matrix core is not affected by fractures, simplifies the operation steps of the existing experimental method, and improves the accuracy of the dynamic imbibition experiment.

The present invention solves its problem and can reach through following technical scheme: this low-permeability fractured reservoir imbibition recovery process experimental method comprises the following steps:

(1) Mold: The mold is composed of side plates, end plates, bottom plates and pressure plates to form a square mold;

(2) Ingredients: the core making material is composed of quartz sand and cement, and the proportion of quartz sand and cement is by weight percentage: 85% to 95% of quartz sand and 5% to 15% of cement;

(3) sand mixing: according to the permeability of the rock core, after the quartz sand is evenly stirred, the medicines required for the preparation of the cement are weighed respectively as required, mixed and poured into the quartz sand, stirred and sieved;

(4) Initial mold loading and pressurization: Wipe the inside of the mold with acetone, put half of the mixed sand into the mold, and then use the sand scraper to move back and forth in the mold along the horizontal direction. During this period, the sand scraper needs to be adjusted continuously Plate depth until the sand is evenly distributed, and finally use the pressure plate to compact the sand, place the filled mold on the pressure testing machine, adjust the position of the mold to keep it on the center line of the pressure bearing plate of the press, and then slowly increase the pressure To the design value, stabilize the pressure for 15 minutes, and release the pressure;

(5) Sulfuric acid paper interlayer: spread the sulfuric acid paper of the designed thickness on the pressed rock core;

(6) Secondary mold loading and pressurization: put the other half of the mixed sand into the mold, use the sand scraper to continuously adjust the depth of the sand scraper until the sand is evenly distributed, use the pressure plate to compact the sand, and finally fill the Put the good mold on the pressure testing machine, adjust the position of the mold to keep it on the center line of the pressure plate of the press, then slowly increase the pressure to the design value, stabilize the pressure for 15 minutes, and release the pressure;

(7) Heating: put the pressed rock core in an oven, and solidify at a constant temperature of 6 to 8 hours at 85°C;

(8) Coring: first cut the massive core according to the designed core length, then take the core from the side with sulfuric acid paper as the center line to obtain a columnar core with a diameter of 2.5 cm, and remove the sulfuric acid paper in the middle of the columnar core to obtain 2 Symmetrical semi-columnar cores are merged to obtain artificially fractured cores;

(9) Evacuate saturated water: weigh the dry weight of the rock core, evacuate and saturate the experimental water, after the saturated water is completed, wipe off the water droplets on the surface of the rock core with test paper, weigh the wet weight of the rock core and calculate the porosity;

(10) Saturated formation crude oil: seal the sides of the two semi-columnar cores with polytetrafluoroethylene raw tape, leave the side faces of the two semi-columnar cores, put them in the core holder after merging, add confining pressure, Saturate formation crude oil and calculate oil saturation, aging for 24 hours; two semi-columnar cores are separated by plastic film in the middle;

(11) Dynamic imbibition test: Take out the core from the core holder, remove the plastic film in the middle of the core and the wrapped polytetrafluoroethylene raw tape, and then cover the arc-shaped outer surface and two end faces of the core with polytetrafluoroethylene raw tape. Tape is re-sealed, only the two sides of the columnar core fractures are exposed, water and oil displacement agent are injected through the core along the fractures, this method is used to simulate the process of imbibition oil recovery in fractured reservoirs, and the effect of imbibition oil recovery and its influencing factors are studied.

Compared with the above-mentioned background technology, the present invention can have the following beneficial effects: the low-permeability fractured reservoir imbibition recovery process experimental method, compared with the existing method, the present invention has the following advantages: (1) simple operation, fracture shape and geometry The size is easy to control; (2) The shape and position of fractures between different cores have good repeatability; (3) The saturation of the core matrix is not affected by the fracture-making process; (4) It can accurately reflect the influence of various factors in the experiment on the dynamic imbibition recovery process ; (5) Core repeatability is excellent.

Description of drawings:

Accompanying drawing 1 is the physical figure of fracture rock core of the present invention;

Accompanying drawing 2 is a schematic diagram of the physical model of cross-seepage flow between fractures and matrix in low-permeability reservoirs;

Accompanying drawing 3 is the relationship curve of imbibition recovery factor and injected oil displacement agent of the present invention.

detailed description:

The present invention will be further described below in conjunction with accompanying drawing:

The experimental method of the process of imbibition recovery in low-permeability fractured reservoirs comprises the following steps:

(1) Mold: the mold is composed of side plates, end plates, base plates and pressing plates to form a square mold. The square mold is equipped with two relative side plates and end plates around the top of the base plate, and two relative side plates and end plate tops There are pressure plates; the side plates and end plates are made of steel, the bottom plate is bakelite, the pressure plate is high-density board, and the two side plates are connected by bolts; the geometric dimensions of the square steel mold: length × width × height = 32cm × 32cm × 10cm;

(2) Ingredients: After the core matrix permeability is determined to be 2mD, the proportions of the amount of quartz sand and cement are determined to be 87% and 13% respectively according to the permeability of the core;

(3) Sand mixing: after stirring 3480g of quartz sand evenly, pour the cement obtained after mixing 385.19g of epoxy resin, 96.30g of dibutyl phthalate, 19.26g of ethylenediamine and 192.59g of acetone Put into quartz sand, stir, sieve; Described quartz sand particle size composition percentage is shown in Table 1:

Table 1 The composition percentage of quartz sand grain size

Particle size (mm) 0.25～0.2 0.2～0.15 0.15～0.1 0.1～0.05 0.05～0.01 percentage(%) 1.0 8.0 42.0 41.0 8.0

(4) Initial mold loading and pressurization: Wipe the inside of the mold with acetone, put half of the mixed sand into the mold, and then use the sand scraper to move back and forth in the mold along the horizontal direction. During this period, the sand scraper needs to be adjusted continuously Plate depth until the sand is evenly distributed, and finally use the pressure plate to compact the sand, place the filled mold on the pressure testing machine, adjust the position of the mold to keep it on the center line of the pressure bearing plate of the press, and then slowly increase the pressure To the design value, stabilize the pressure for 15 minutes, and release the pressure;

(5) Sulfuric acid paper interlayer: spread the sulfuric acid paper of the designed thickness on the pressed rock core;

(6) Secondary mold loading and pressurization: put the other half of the mixed sand into the mold, use the sand scraper to continuously adjust the depth of the sand scraper until the sand is evenly distributed, use the pressure plate to compact the sand, and finally fill the Put the good mold on the pressure testing machine, adjust the position of the mold to keep it on the center line of the pressure plate of the press, then slowly increase the pressure to the design value, stabilize the pressure for 15 minutes, and release the pressure;

(7) Heating: put the pressed rock core in an oven, and solidify at a constant temperature of 6 to 8 hours at 85°C;

(8) Coring: first cut the massive core according to the designed core length, then take the core from the side with sulfuric acid paper as the center line to obtain a columnar core with a diameter of 2.5 cm, and remove the sulfuric acid paper in the middle of the columnar core to obtain 2 Symmetrical semi-columnar cores are combined to obtain artificial fracture cores (as shown in Figure 1);

(9) Evacuate saturated water: weigh the dry weight of the rock core, evacuate and saturate the experimental water, after the saturated water is completed, wipe off the water droplets on the surface of the rock core with test paper, weigh the wet weight of the rock core and calculate the porosity;

(10) Saturated formation crude oil: Use polytetrafluoroethylene raw tape to seal the sides of the two semi-columnar cores (leaving the end faces), and then combine them. The middle of the sides of the two semi-columnar cores is isolated with a plastic film, because the plastic film itself has no Permeability, and can closely fit the core section under the action of confining pressure, crude oil can only pass through the end face of the core, thus ensuring that the oil saturation of the fractured core matrix is not affected by the fracture; after merging, put it in the core holder, and add Confining pressure, saturate formation crude oil and calculate oil saturation, aging for 24h;

(11) Dynamic imbibition test: Take out the core from the core holder, remove the plastic film in the middle of the core and the wrapped polytetrafluoroethylene raw tape, and then cover the arc-shaped outer surface and two end faces of the core with polytetrafluoroethylene raw tape. The adhesive tape was re-sealed, only the two sides of the columnar core fractures were exposed, and the oil displacement agent was passed through the core along the fractures at an injection rate of 0.05mL/min, and the dynamic imbibition experiment was carried out, as shown in Figure 2; according to the cumulative oil production at the outlet at different times Calculate the dynamic imbibition recovery under different injection rates, and draw the corresponding graphs (see Fig. 3).

The existing experimental method is to first process the core with saturated formation water and formation crude oil, then cut the core to create fractures or use a triaxial rock mechanics instrument to apply external force to create fractures, and finally carry out dynamic imbibition experiments. Compared with the existing experimental method, the present invention does not need to use external force to create fractures, and the fractured cores can be obtained by separately pressing the cores and laying sulfuric acid paper interlayers with a set thickness, which not only simplifies the experimental operation, but also ensures the fracture shape and The location has good repeatability; by using plastic film and PTFE raw tape in the process of oil saturation, the oil saturation of the matrix core is not affected by fractures, thereby avoiding the influence of external fractures on the matrix saturation; The fracture shape, size, location, and core matrix saturation have good repeatability, so this method is conducive to accurately reflecting the influence of various factors in the experiment on the dynamic imbibition recovery process.

The above experimental steps (10) and (11) were carried out at a temperature of 83.3°C in the Fuyu oil layer of Daqing Toutai Oilfield; the oil used in the experiment was taken from Well Mao 503 in Block Mao 503 of Daqing Toutai Oilfield, and the viscosity was 4.2 mPa·s at 83.3°C The oil displacement agent used in the experiment is a mass concentration of 0.2% Davis surfactant solution, and the Davis surfactant is produced by Dalian Davis Chemical Agent Co., Ltd., with an effective content of 40%, and the prepared water is Daqing Toutai Oilfield Fill with water.

Claims (3)

1. A low-permeability fractured reservoir imbibition oil recovery experimental method is characterized in that: comprises the following steps: (1) Mold: The mold is composed of side plates, end plates, bottom plates and pressure plates to form a square mold; (2) Ingredients: the core making material is composed of quartz sand and cement, and the ratio of quartz sand and cement is by weight percentage: 85%~95% of quartz sand, 5%~15% of cement; The cement is composed of epoxy resin and three additives, dibutyl phthalate, ethylenediamine, and acetone, and the proportion of epoxy resin and three additives is by weight: 385.19 parts of epoxy resin, phthalate 96.30 parts of dibutyl formate, 19.26 parts of ethylenediamine and 192.59 parts of acetone; (3) sand mixing: according to the permeability of the rock core, after the quartz sand is evenly stirred, the medicines required for the preparation of the cement are weighed respectively as required, mixed and poured into the quartz sand, stirred and sieved; (4) Initial mold loading and pressurization: Wipe the inside of the mold with acetone, put half of the mixed sand into the mold, and then use the sand scraper to move back and forth in the mold along the horizontal direction. During this period, the sand scraper needs to be adjusted continuously Plate depth until the sand is evenly distributed, and finally use the pressure plate to compact the sand, place the filled mold on the pressure testing machine, adjust the position of the mold to keep it on the center line of the pressure bearing plate of the press, and then slowly increase the pressure To the design value, stabilize the pressure for 15 minutes, and release the pressure; (5) Sulfuric acid paper interlayer: spread the sulfuric acid paper of the designed thickness on the pressed rock core; (6) Secondary mold loading and pressurization: put the other half of the mixed sand into the mold, adjust the depth of the sand scraper continuously with a sand scraper until the sand is evenly distributed, compact the sand with a pressure plate, and finally fill the Put the good mold on the pressure testing machine, adjust the position of the mold to keep it on the center line of the pressure plate of the press, then slowly increase the pressure to the design value, stabilize the pressure for 15 minutes, and release the pressure; (7) Heating: put the pressed rock core in an oven, and solidify at a constant temperature of 6 to 8 hours at 85°C; (8) Coring: first cut the massive core according to the designed core length, then take the core from the side with sulfuric acid paper as the center line to obtain a columnar core with a diameter of 2.5 cm, and remove the sulfuric acid paper in the middle of the columnar core to obtain 2 Symmetrical semi-columnar cores are merged to obtain artificially fractured cores; (9) Evacuate saturated water: weigh the dry weight of the rock core, evacuate and saturate the experimental water, after the saturated water is completed, wipe off the water droplets on the surface of the rock core with test paper, weigh the wet weight of the rock core and calculate the porosity; (10) Saturated formation crude oil: seal the sides of the two semi-columnar cores with polytetrafluoroethylene raw tape, leave the side faces of the two semi-columnar cores, put them in the core holder after merging, add confining pressure, Saturate formation crude oil and calculate oil saturation, aging for 24 hours; two semi-columnar cores are separated by plastic film in the middle; (11) Dynamic imbibition test: Take out the core from the core holder, remove the plastic film in the middle of the core and the wrapped polytetrafluoroethylene raw tape, and then cover the arc-shaped outer surface and two end faces of the core with polytetrafluoroethylene raw tape. Tape is re-sealed, only the two sides of the columnar core fractures are exposed, water and oil displacement agent are injected through the core along the fractures, this method is used to simulate the process of imbibition oil recovery in fractured reservoirs, and the effect of imbibition oil recovery and its influencing factors are studied. 2. The experimental method for imbibition recovery in low-permeability fractured reservoirs according to claim 1, characterized in that: two opposite side plates and end plates are placed around the top of the bottom plate, and the two opposite side plates and end plates There is a pressure plate on the top of the plate; the side plate and the end plate are made of steel, the bottom plate is bakelite, and the pressure plate is a high-density board. 3. The experimental method for imbibition recovery of low-permeability fractured reservoirs according to claim 1 or 2, characterized in that: the geometric dimensions of the square mold are: length×width×height=32cm×32cm×10cm.