CN109001097A - A kind of spontaneous imbibition research device of visualization fracturing fluid and method - Google Patents

Abstract

The invention relates to a device and method for visualizing the spontaneous imbibition of fracturing fluid. The device includes a booster pump, a first burette, a second burette, a core slice and a vacuum pump; the inlet end of the core slice is connected to one end of the first burette, and the core The outlet end of the slice is connected to one end of the second burette; when the core slice is evacuated, the other end of the second burette is connected to the vacuum pump; when the core slice is driven forward, the other end of the first burette is connected to the pressurized The pump is connected; when the rock core slice is reverse-driven, the other end of the second burette is connected with the booster pump. This device can simulate the entire process of hydraulic fracturing to study the spontaneous imbibition of fracturing fluid. During the simulation The phenomenon of spontaneous imbibition can be observed and recorded by naked eyes and optical microscope equipment, and finally the characteristics of spontaneous imbibition of fracturing fluid can be obtained qualitatively and quantitatively.

Description

A visual fracturing fluid spontaneous imbibition research device and method

technical field

The invention relates to the technical field of oil and gas reservoir development, in particular to a device and method for researching the spontaneous imbibition of visualized fracturing fluid.

Background technique

With the increasing dependence of human beings on resources such as oil and natural gas, in the past decade, unconventional oil and gas extraction has gradually become the main task of oil and gas development in countries all over the world. Generally speaking, unconventional oil and gas resources have the characteristics of large resources but difficult exploitation. In order to form industrial oil and gas flow, unconventional oil and gas resources must carry out production stimulation operations different from conventional oil and gas resources. Hydraulic fracturing is one of the important means of exploiting unconventional oil and gas resources.

Usually after hydraulic fracturing, the fracturing fluid needs to be reversed quickly to prevent the fracturing fluid from causing damage to the reservoir, and after the fracturing fluid is reversed, oil and gas will be brought out so that the fracturing well can be put into production quickly. However, the situation in the field is exactly the opposite of the above cognition: after fracturing some tight sandstone reservoirs, the fracturing fluid flow rate of many wells is extremely low, but the production is very high, and the fracturing fluid flow rate of a few wells is very high. High, but the single well production is relatively low.

Imbibition refers to the process of spontaneous inhalation of a certain wetting fluid by a porous medium, and since the power of imbibition mainly comes from capillary force, spontaneous imbibition mostly occurs in tight reservoirs. As a result, the non-reversed fracturing fluid in the tight reservoir imbibed to displace the crude oil, which led to the above phenomenon on site.

Most of the existing spontaneous imbibition research methods are to study the spontaneous imbibition of water into the core to displace crude oil. In recent years, there are also many experimental methods that take surfactants, various chemical reagents and formation conditions into consideration. However, there are few research methods that can completely display the entire spontaneous imbibition process and study the spontaneous imbibition phenomenon of fracturing fluid during hydraulic fracturing.

Contents of the invention

The present invention aims at the defects existing in the existing spontaneous imbibition research methods, such as the inability to allow researchers to visually observe the entire imbibition process, and almost no research methods to study the imbibition of fracturing fluids, and proposes a visual fracturing fluid spontaneous imbibition Apparatus and method for osmosis research. The invention aims at studying the spontaneous imbibition of fracturing fluid, and enables researchers to observe the phenomenon of spontaneous imbibition intuitively, and finally obtain the situation of spontaneous imbibition of fracturing fluid qualitatively or even quantitatively.

In order to achieve the above object, the present invention adopts the following technical solutions:

A visual fracturing fluid spontaneous imbibition research device, including a booster pump, a first burette, a second burette, a core slice and a vacuum pump; the inlet end of the core slice is connected to one end of the first burette, and the outlet end of the core slice is connected to the second end One end of the two burets is connected;

When vacuumizing the rock core slice, the other end of the second burette is connected with the vacuum pump;

When the core slice is positively driven, the other end of the first burette is connected to the pressurizing pump;

When the rock core thin section is reverse driven, the other end of the second burette is connected with a pressurizing pump.

Preferably, the forward drive refers to driving the core slice by pressing the inlet end of the core slice; the reverse drive refers to driving the core slice by pressurizing the core slice from the outlet end, the present invention In the following methods, vacuum pumping, saturated water, saturated oil and fracturing fluid flooding are all in the form of forward drive; oil reverse flooding with fracturing fluid is in the form of reverse drive.

Preferably, it also includes an observation component, the observation component includes an optical microscope and an electronic computer, the optical microscope and the electronic computer are connected, and the rock core slice is arranged at the center of the field of view of the optical microscope.

Preferably, the inlet end of the core slice is connected to the first burette through a rubber hose.

Preferably, the outlet end of the core slice is connected to the second burette through a rubber hose.

Preferably, the first burette is connected to the booster pump through a rubber hose.

Preferably, the rubber hose is a butadiene rubber hose.

A method for researching the spontaneous imbibition of visual fracturing fluid, carried out by the above-mentioned device, comprising the following steps:

(1) Vacuuming: the first burette is filled with water, and the second burette is empty; the passage between the first burette and the inlet end of the rock core sheet is cut off, and the rock core sheet is evacuated by a vacuum pump;

(2) Saturated water: after vacuuming, the passage between the second burette and the vacuum pump is cut off; the passage between the first burette 3 and the inlet end of the rock core slice is connected; the rock core of the rock core slice is saturated with water, and the rock core is When there is no obvious change in color, stop the saturated water;

(3) Saturated oil: replace the first burette with an oil-containing burette, and replace the second burette with an empty burette; pressurize the oil-containing burette through a pressurizing pump to make the oil enter the rock core slice; When the empty buret connected to the outlet end of the oil outlet and the core color does not change, stop the saturated oil;

(4) Fracturing fluid flooding: replace the burette connected to the inlet end of the core slice with a burette containing fracturing fluid, and replace the burette connected to the outlet end of the core slice with an empty burette; Pressurize the burette of the fluid to make the fracturing fluid enter the core slice; when the empty burette connected to the outlet end of the core slice comes out of the fracturing fluid and the color of the core remains unchanged, the fracturing fluid flooding is terminated;

(5) Oil reverse drive fracturing fluid: Replace the burette connected to the outlet end of the core slice with an oil-containing burette, and replace the burette connected to the inlet end of the core slice with an empty burette; pressure to make the oil back drive the fracturing fluid in the core slice; when the empty burette connected to the inlet end of the core slice comes out of oil and the core color does not change, the oil back drive fracturing fluid is ended; during the oil back drive fracturing fluid process observe the phenomenon of spontaneous imbibition;

(6) Calculate the percentage of residual fracturing fluid in the spontaneous imbibition core of fracturing fluid.

Preferably, in the step (6), the process of calculating the residual fracturing fluid percentage of the spontaneous imbibition core of the fracturing fluid is as follows:

Calculate the retention of fracturing fluid in the core slice through the scales of the burettes at both ends of the core slice;

Subtract the water yield in the first burette after the saturated water finishes from the first burette water yield when the saturated water begins in step (2), then subtract the water yield in the second burette after the saturated water finishes, obtain the water yield L1 that enters the rock core sheet;

The amount of oil in the buret connected to the outlet end after the saturated oil is subtracted from the amount of oil in the burette that contains the oil when the saturated oil begins in step (3), obtains the amount of oil O that enters the rock core slice;

Enter the water yield L1 in the rock core slice in the step (2) and subtract the water yield in the burette connected to the outlet end in the step (3), obtain the water yield L2 in the rock core slice after the saturated oil finishes;

From the amount of fracturing fluid in the burette containing fracturing fluid at the beginning of the fracturing fluid flooding in step (4) minus the amount of water in the burette connected to the outlet after the fracturing flooding ends, plus the amount of water in the core slice after the saturated oil is over. The amount of water L2 is obtained to obtain the amount of fracturing fluid F1 retained in the core slice;

Step (3) enters the oil quantity O1 in the rock core sheet minus the oil quantity of the burette connected to the outlet end in the step (4), to obtain the oil quantity O2 in the rock core sheet after the fracturing fluid flooding finishes;

Subtract the oil volume in the buret connected to the outlet end of the oil reverse drive fracturing fluid from the oil volume in the burette connected to the outlet end at the beginning of the oil reverse drive fracturing fluid in step (5), and add the oil volume in the burette connected to the inlet end after the oil reverse drive fracturing fluid ends, plus step (4) The oil amount O2 in the post-rock core slice is obtained after the oil reverse drive fracturing fluid is finished. The oil amount O3 in the rock core slice;

Subtract the amount of fracturing fluid in the burette connected to the inlet end in step (5) from the amount of fracturing fluid F1 entering the core slice after step (4) is completed, and obtain the fracturing fluid in the core slice after the end of the oil reverse drive fracturing fluid F2, the percentage of residual fracturing fluid in the fracturing fluid spontaneously imbibed core is

Preferably, in the step (1), the water contained in the first burette is a sample prepared according to the water properties of the target formation, and methylene blue is added to the water to make it blue;

In the step (4), the fracturing fluid is a sample prepared from a hydraulic fracturing construction fracturing fluid formula, and methylene blue is added to the fracturing fluid to make it blue;

In the step (5), the oil is kerosene, and oil-soluble red is added to the kerosene to make it red.

Preferably, in the step (6), the process of calculating the residual fracturing fluid percentage of the spontaneous imbibition core of the fracturing fluid is as follows:

Step 6.1, from the start of step (1) vacuuming to the end of step (5) oil reverse drive fracturing fluid, take photos of the core slices during the operation of steps (1) to (5) through an optical microscope, and take photos of steps (2) to Step (5) the full field of view after each step ends, and the optical microscope sends the image taken to the electronic computer;

In step 6.2, the electronic computer characterizes the oil-water color in the image through different thresholds to obtain the chromatogram of the full-view image;

Step 6.3, the electronic computer analyzes the residual water according to the chromatogram, and obtains the blue area F ₁ ' of step (4) fracturing fluid flooding process, and the blue area F of step (5) oil reverse flooding fracturing fluid process ₂ ′, and calculate the percentage of residual fracturing fluid in the spontaneous imbibition core of fracturing fluid as

Preferably, in the step (1), the time for vacuuming is 5 to 10 hours;

In the step (2), the time for the core of the core slice to be saturated with water is 2 to 3 hours;

In the step (3), the pressure pump pressurizes the burette containing oil for 5 to 8 hours;

In the step (4), the booster pump pressurizes the burette containing the fracturing fluid for 5 to 8 hours;

In the step (5), the pressurization time of the burette containing the oil of the pressurizing pump is 5 to 8 hours.

Preferably, in the step (3), the pressure of the booster pump to pressurize the burette containing oil is 0.02-0.20MPa;

In the step (4), the pressurizing pump pressurizes the burette containing the fracturing fluid at a pressure of 0.02-0.20 MPa;

In the step (5), the pressurizing pump pressurizes the burette containing oil with a pressure of 0.02-0.20 MPa.

Preferably, from step (3) to step (5), after each step is completed, the core slices are placed for 6-12 hours to age the core slices.

The beneficial effects of the patent of the present invention are:

The visual fracturing fluid spontaneous imbibition research device of the present invention connects the first burette and the second burette respectively at the inlet end and the outlet end of the rock core slice, and when vacuumizing the rock core slice, the other end of the second burette is connected to a vacuum pump; When the core slice is driven forward, the other end of the first burette is connected to the booster pump; when the core slice is driven backward, the other end of the second burette is connected to the booster pump; therefore, it is possible to The flow and imbibition of the fluid can be seen intuitively with the naked eye, making up for the defects that the existing technology cannot directly observe. In addition, the spontaneous imbibition of the core can be quantitatively measured through the burette, and finally qualitative and even Quantitatively obtain the situation of spontaneous imbibition of fracturing fluid, from which the influence of spontaneous imbibition of fracturing fluid on production can be obtained.

Further, the present invention can take real-time full-view images of rock core slices through an optical microscope, and the electronic computer analyzes and processes the full-view images to obtain the chromatograms of the full-view images, and the electronic computer obtains the corresponding color thresholds according to different color thresholds. Area, so as to obtain the residual amount of fracturing fluid imbibition and the percentage of residual fracturing fluid imbibition; the present invention records and analyzes through optical microscope and computer, and can visually see the occurrence of fluid flow and imbibition phenomenon. In addition, the computer can also be used to quantitatively calculate the amount of fracturing fluid remaining in the core slices, and thus the influence of fracturing fluid spontaneous imbibition on production can be obtained.

In the research method of visual fracturing fluid spontaneous imbibition of the present invention, when studying fracturing fluid spontaneous imbibition, it is considered that the fracturing fluid cannot be taken out for imbibition experiments alone, but the entire change of formation fluid during hydraulic fracturing must be simulated Therefore, four main steps of saturated water, saturated oil, fracturing fluid flooding and oil reverse flooding fracturing fluid are designed, which respectively represent that the original formation pores are occupied by formation water first, and formation pores are then occupied by formation water after oil generation. Crude oil occupies, until the fracturing fluid displaces crude oil to occupy the pores during the subsequent fracturing operation, and the crude oil reverses the fracturing fluid in the final production. The four processes from the water occupying the pores to the oil well output are completely and systematically simulated. The process makes the research closer to reality and more comprehensive.

Description of drawings

Fig. 1 is an overall schematic diagram of an embodiment of the visual fracturing fluid spontaneous imbibition research device of the present invention;

Fig. 2 is the schematic diagram of rock core slice of the present invention;

Fig. 3 is the schematic flow sheet of research method of the present invention;

Fig. 4 is the whole view figure that optical microscope of the present invention shoots;

Fig. 5 is the chromatogram obtained by the electronic computer of the present invention.

Icon description: 1-pressurizing pump, 2-rubber hose, 3-first burette, 3-1-second burette, 4-core slice, 5-vacuum pump, 6-optical microscope, 7-electronic computer, A- Inlet port; B-exit port.

Detailed ways

In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Apparently, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Referring to Fig. 1 and Fig. 2, the visual fracturing fluid spontaneous imbibition research device of the present invention comprises a booster pump 1, a first burette 3, a second burette 3-1, a core slice 4 and a vacuum pump 5; the entrance of the core slice 4 End A is connected with one end of the first burette 3, and the outlet port B of the core slice 4 is connected with one end of the second burette 3-1;

Referring to Fig. 3, when the rock core slice 4 is vacuumized, the other end of the second burette 3-1 is connected with the vacuum pump 5;

When the rock core slice 4 is positively driven, the other end of the first burette 3 is connected with the pressurizing pump 1;

When the core slice 4 is reversely driven, the other end of the second burette 3 - 1 is connected with the pressurizing pump 1 .

With reference to Fig. 3, in the present invention, forward drive refers to that the inlet end A of rock core sheet 4 pressurizes core sheet 4 and drives; In the following method of the present invention, vacuuming, saturated water, saturated oil and fracturing fluid flooding are all in the form of forward driving; oil reverse driving fracturing fluid is in the form of reverse driving.

As shown in Figure 1, as a preferred embodiment of the present invention, the visual fracturing fluid spontaneous imbibition research device of the present invention also includes an observation assembly, the observation assembly includes an optical microscope 6 and an electronic computer 7, and the optical microscope 6 and the electronic computer 7 are connected , the core slice 4 is set at the center of the field of view of the optical microscope 6 . The optical microscope 6 of the present invention can be connected with an electronic computer 7 for subsequent experiment recording and data processing. Above-mentioned optical microscope 6 has the characteristic that can match with computer system and software. The computer software mentioned above is software that can distinguish image pigments, including but not limited to Photoshop software and Nikon Nis-Elements Documentation software.

Referring to FIG. 1 , as a preferred embodiment of the present invention, the inlet port A of the core slice 4 is connected to the first burette 3 through a rubber hose 2 . The outlet end B of the core slice 4 is connected with the second burette 3 - 1 through a rubber hose 2 . The first burette 3 is connected with the pressurizing pump 1 through a rubber hose 2 .

As a preferred embodiment of the present invention, the rubber hose 2 at both ends of the core slice is made of a material that is resistant to high pressure and not easily deformed.

The visual fracturing fluid spontaneous imbibition research method of the present invention comprises the following steps in sequence:

Fabrication of basic experimental materials: As shown in Figure 2, after the core is obtained, the core is made into a core sheet 4, and a certain length of high-pressure-resistant and non-deformable rubber hose 2 is connected to the inlet A and outlet B of the core sheet 4 respectively. Formation water samples were prepared according to the formation water properties of the target formation, and then methylene blue was added to the formation water samples to make the formation water samples blue; Add methylene blue to make the fracturing fluid sample blue; take kerosene sample as formation oil, add oil-soluble red to the kerosene to make the kerosene red;

(2) vacuuming: as shown in step 1 in Fig. 2, the inlet end A of rock core sheet 4 is connected with the burette that fills water, and the outlet end B of rock core sheet 4 is connected with empty burette and vacuum pump 5, and then Check the airtightness of the connected overall structure. After the inspection is completed, if the tightness is good, the core slice 4 is placed in the center of the field of view of the optical microscope 6, the optical microscope 6 is opened and connected to the electronic computer 7, and the system connection is checked. Finally, clamp the rubber hose 2 at the joint between the rock core slice 4 and the burette filled with water with sealing pliers, turn on the vacuum pump 5, and vacuumize the rock core slice 4 for 5-10 hours;

(3) Saturated water: As shown in step 2 in Figure 2, after vacuuming, clamp the rubber hose 2 at the connection between the core sheet 4 and the vacuum pump 5 with sealing pliers, close and remove the vacuum pump 5. Open the rubber hose 2 at the connection between the rock core sheet 4 and the water burette (the burette that is connected to the inlet port A) to make the rock core saturated with water, and when the color of the rock core does not change significantly, end the saturated water. Usually saturated with water for 2-3 hours, after the saturation is completed, place the core slices for 6-12 hours to age. This process simulates the process that water first fills rock pores under original formation conditions;

(4) Saturated oil: as shown in step 3 in Fig. 2, change the burette connected with rock core slice 4 inlet port A into a burette containing oil, and change the burette connected with outlet port B into an empty burette. Then connect the oil-containing burette at the inlet end A of the core slice 4 to the booster pump 1 and start to pressurize gradually, so that the oil in the burette connected with the inlet end A gradually enters the core slice 4 . After the empty burette connected to outlet B has been discharged for a period of time and the color of the core has no obvious change, stop the saturated oil. The said oil flow out for a period of time and the color of the core changes without name means: the liquid from the empty buret connected to the outlet port B is always the liquid in the pressurized inlet end buret, and the red area and blue area in the core slice 4 are no longer Variety. Usually saturated with oil for 5-8 hours, after the saturation is completed, place the core slices for 6-12 hours to age. This process simulates the process of oil flooding to replace water to occupy pores after oil and gas are produced in the formation;

(5) Fracturing fluid flooding: as shown in step 4 in Fig. 2, at this moment, the burette connected to the inlet port A of the rock core sheet 4 is replaced with a burette containing fracturing fluid, and the buret connected with the outlet port is replaced with an empty one The burette is used to pressurize the fracturing fluid in the burette connected to the inlet port A so that the fracturing fluid enters the core slice 4 . When the buret connected to the outlet port B has fracturing fluid flowing out for a period of time and the color of the core has no obvious change, the fracturing fluid flooding is ended. Usually the oil displacement is 5-8 hours, and the core slices are placed for 6-12 hours after the fracturing fluid flooding is completed to age them. This process simulates the process of fracturing fluid entering the formation pores to drive away crude oil during the development process;

(6) Oil reverse drive fracturing fluid: As shown in step 5 in Figure 2, replace the burette connected to the outlet port B with an oil-containing burette, replace the burette connected to the inlet port A with an empty burette, and replace the outlet The oil-containing burette connected to port B is connected to booster pump 1, and the outlet port is reversely pressurized by booster pump 1, so that the oil in the oil-containing burette connected to outlet port B is counter-driven with fracturing fluid. When the empty burette connected to the inlet port A comes out of oil for a period of time and the color of the core remains unchanged for a long time, the oil reverse flooding fracturing fluid ends. Usually back flooding takes 5-8 hours, and after the back flooding is completed, place the core slices for 6-12 hours to age them. This process simulates the process of oil entering the wellbore after hydraulic fracturing;

The gradual pressurization of the fracturing fluid sample or kerosene in the above steps (4)-(6) is firstly pressurized with a small constant pressure by the pressurizing pump 1, and then gradually pressurized. The minimum pressure should not be lower than 0.02MPa, and the maximum pressure should not exceed 0.20MPa. Each section of pressurization time is 1-2 hours.

(7) Observe the phenomenon of spontaneous imbibition and record the data during the experiment, as follows:

Observation with the naked eye: It can be clearly seen by the naked eye that the blue liquid or red liquid enters the core sheet 4 to occupy a certain space, and there is still a small amount of color change after it is generally stable, until there is no color change at last;

Observation through optical microscope: This is also the main observation method. Using optical microscope 6, you can zoom in on local observation, and you can clearly see that water or oil or fracturing fluid occupies and moves out of core pores, and you can even observe things that are difficult to observe with the naked eye. When the fracturing fluid enters the core thin slice 4, the spontaneous imbibition phenomenon that the fracturing fluid enters the tiny pores to drive out the oil occurs. At the same time, the optical microscope 6 is connected to the electronic computer 7, and the optical microscope 6 can photograph or record the entire experimental research process for subsequent analysis and calculation.

(8) Calculate and process the data to obtain the residual fracturing fluid percentage of the fracturing fluid spontaneously imbibing the core. This step is divided into the following two situations (a) and (b):

(a) Manual measurement method: this method calculates the holdup of fracturing fluid in the rock core slice 4 by the scale of the burette at both ends of the core slice 4:

1. subtract the water yield in the first burette after the saturated water finishes from the first burette water yield when the saturated water begins in step (3), then subtract the water yield in the second burette after the saturated water finishes, obtain the water yield L1 that enters the rock core sheet;

2. subtract the oil quantity in the burette connected to the outlet end after the saturated oil ends from the oil quantity in the burette that contains oil when the saturated oil begins in step (4), obtain the oil quantity O that enters the rock core slice;

3. enter the water yield L1 in the rock core slice in the step (3) and subtract the water yield in the burette connected to the outlet end in the step (4), obtain the water yield L2 in the rock core slice after the saturated oil finishes;

④ From the amount of fracturing fluid in the burette containing fracturing fluid at the beginning of the fracturing fluid flooding in step (5) minus the amount of water in the buret connected to the outlet end after the fracturing flooding is completed, plus the amount of the core slice after the end of saturated oil The amount of water L2 in the core is obtained to obtain the amount of fracturing fluid F1 retained in the core slice;

5. enter the oil quantity O1 in the rock core slice in the step (4) and subtract the oil quantity of the burette connected at the outlet end in the step (5), obtain the oil quantity O in the rock core slice after the fracturing fluid flooding finishes;

⑥ Subtract the oil volume in the burette connected to the outlet end of the oil reverse drive fracturing fluid from the oil volume in the burette connected to the outlet end at the beginning of the oil reverse drive fracturing fluid in step (6), and add the oil volume in the burette connected to the inlet end after the oil reverse drive fracturing fluid ends, plus step (5) The oil amount O2 in the core slice after the end is obtained, and the oil amount O3 in the core slice after the end of the oil reverse drive fracturing fluid is obtained;

⑦ Subtract the amount of fracturing fluid in the buret connected to the inlet end in step (6) from the amount of fracturing fluid F1 entering the core slice after step (5) is completed, and the fracturing fluid in the core slice after the end of the oil reverse drive fracturing fluid is If the fluid volume is F2, then the percentage of residual fracturing fluid in the core that the fracturing fluid spontaneously imbibes is (b) Chromatography method: Referring to Figure 4 and Figure 5, this method records the entire spontaneous imbibition process of fracturing fluid through an optical microscope 6 and an electronic computer 7, and the different color differences of the core slice 4—the blue area represents fracturing fluid (the fracturing fluid saturated area as shown in Figure 5), the red area represents the oil (the oil-saturated area as shown in Figure 5), and the green area represents the unoccupied empty pores (the unsaturated area in Figure 5 area), to determine the spontaneous imbibition holdup of fracturing fluid. It is fast and accurate, and the process is as follows:

①Start vacuuming in step (2), turn on the computer software in the optical microscope 6 and electronic computer 7 to start recording the entire experimental process, and take pictures of the full view of the rock core slice 4 after each step from step (3) to step (6) Image, as shown in Figure 4;

② Import the full view image of the core slice 4 in step (5) and step (6) into the computer software. Since different colors have different thresholds, the computer software uses different thresholds to describe the color of oil and water to obtain the full view image The chromatogram, as shown in Figure 5;

③The electronic computer analyzes the residual water according to the chromatogram, and obtains the blue area F ₁ ′ of step (5) fracturing fluid flooding process, and the blue area F ₂ ′ of step (6) oil reverse flooding fracturing fluid process . And calculate the residual fracturing fluid percentage of fracturing fluid spontaneous imbibition core by computer

The above-mentioned research steps adopted in the present invention can completely simulate the entire hydraulic fracturing process, display the local fracturing fluid imbibition of the formation, and the whole process can be visualized and quantified. Step (3) Simulate the process of water filling the rock pores under the original formation conditions; Step (4) simulate the process of oil flooding to replace water to occupy the pores after oil and gas are produced in the formation; Step (5) simulate the process of fracturing fluid entering the formation pores to drive In the process of carrying crude oil, step (6) simulates the process of oil entering the wellbore after hydraulic fracturing; while using thin core slices 4 instead of whole cores for research, the whole process can be visualized and spontaneous imbibition phenomena can be observed; The burette and optical microscope with metering function can effectively measure the amount of liquid entering and discharging the core slice, so that the percentage of fracturing fluid imbibition and retention can be calculated.

In the present invention, step (2) is evacuated for at least 5 hours, and if the core is relatively dense, it is recommended to evacuate for 10 hours.

In step (3), when the color of the core slice does not change significantly, it means that the formation water sample dyed by methyl blue completely enters the vacuumed core slice, and the blue area of the core slice no longer increases.

From step (4) to step (6), the discharge of liquid from the end of the hollow burette for a period of time means: the discharge of the liquid from the empty burette connected to the outlet port B has always been the liquid in the burette at the pressurized inlet end, and the oil and water in the core slice have reached a balance; When there is no obvious change in color, it means that the red area and blue area in the core thin section are relatively stable. Only when the above two conditions are met can the step be considered complete.

After each step from step (3) to step (6) is completed, it is recommended to place the core slices for 6-12 hours to age the core slices, which can better simulate the real formation conditions.

To sum up, a visual fracturing fluid spontaneous imbibition research device and method proposed by the present invention aims to study the spontaneous imbibition of fracturing fluid, and can simulate the entire hydraulic fracturing process, so that researchers can see through the naked eye and optical microscope The equipment visually observes the phenomenon of spontaneous imbibition, and finally obtains the situation of spontaneous imbibition of fracturing fluid qualitatively and quantitatively.

Claims (10)

1. a kind of spontaneous imbibition research device of visualization fracturing fluid, which is characterized in that including force (forcing) pump (1), the first buret (3), the second buret (3-1), core wafer (4) and vacuum pump (5)；The arrival end (A) and the first buret of core wafer (4) (3) one end connection, the outlet end (B) of core wafer (4) is connect with one end of the second buret (3-1)；

When vacuumizing to core wafer (4), the other end of the second buret (3-1) is connect with vacuum pump (5)；

When carrying out forward driving to core wafer (4), the other end of the first buret (3) is connect with force (forcing) pump (1)；

When being driven in the reverse direction to core wafer (4), the other end of the second buret (3-1) is connect with force (forcing) pump (1).

2. a kind of spontaneous imbibition research device of visualization fracturing fluid according to claim 1, which is characterized in that further include seeing Component is surveyed, observation component includes optical microscopy (6) and electronic computer (7), optical microscopy (6) and electronic computer (7) Connection, core wafer (4) are set to the sighting center of optical microscopy (6).

3. a kind of spontaneous imbibition research device of visualization fracturing fluid according to claim 1, which is characterized in that core wafer (4) arrival end (A) is connect with the first buret (3) by rubber hose (2)；The outlet end (B) and second of core wafer (4) Buret (3-1) is connected by rubber hose (2)；First buret (3) is connect with force (forcing) pump (1) by rubber hose (2).

4. a kind of spontaneous imbibition research method of visualization fracturing fluid, which is characterized in that by described in claim 1-3 any one The spontaneous imbibition research device of visualization fracturing fluid carry out, comprising the following steps:

(1) it vacuumizes: water will be filled in the first buret (3), the second buret (3-1) is sky；By the first buret (3) and rock core Access cut-off between the arrival end (A) of thin slice (4), vacuumizes core wafer (4) by vacuum pump (5)；

(2) saturated water: after exhausting vacuum, the access between the second buret (3-1) and vacuum pump (5) is ended；Conducting first Access between buret (3) and the arrival end (A) of core wafer (4)；The rock core saturated water for making core wafer (4), to rock core When color is without significant change, terminate saturated water；

(3) saturated oils: it will be changed to the buret containing oil in the first buret (3), the second buret (3-1) is changed to sky Buret；It is pressurizeed by force (forcing) pump (1) to the buret containing oil, enters oil in core wafer (4)；To core wafer (4) when the empty buret of outlet end (B) connection is fuel-displaced and rock core color is unchanged, terminate saturated oils；

(4) buret that the arrival end (A) of core wafer (4) connects the fracturing fluid displacement of reservoir oil: is changed to the titration containing fracturing fluid The buret that the outlet end (B) of core wafer (4) connects is changed to empty buret by pipe；By force (forcing) pump (1) to containing pressure The buret pressurization for splitting liquid, enters fracturing fluid in core wafer (4)；The sky that outlet end (B) to core wafer (4) connects When buret goes out fracturing fluid and unchanged rock core color, terminate the fracturing fluid displacement of reservoir oil；

(5) oil is anti-drives fracturing fluid: the buret that the outlet end (B) of core wafer (4) connects is changed to the buret containing oil, The buret that the arrival end (A) of core wafer (4) connects is changed to empty buret；Drop by force (forcing) pump (1) containing oil Determine pipe pressurization, makes the oily anti-fracturing fluid driven in core wafer (4)；The empty titration that arrival end (A) to core wafer (4) connects Manage fuel-displaced and rock core color it is unchanged when, terminate that oil is anti-to drive fracturing fluid；It is existing that spontaneous imbibition is observed during oily anti-drive fracturing fluid As；

(6) the spontaneous imbibition rock core remnants fracturing fluid percentage of fracturing fluid is calculated.

5. a kind of spontaneous imbibition research method of visualization fracturing fluid according to claim 4, which is characterized in that the step (6) in, the process for calculating the spontaneous imbibition rock core remnants fracturing fluid percentage of fracturing fluid is as follows:

The first buret (3) water subtracts the water after saturated water in the first buret (3) when by step (2) saturated water Amount, then the water after saturated water in the second buret (3-1) is subtracted, obtain the water L1 into core wafer (4)；

Contain outlet end (B) after the oil mass in the buret of oil subtracts saturated oils when by step (3) saturated oils to connect Buret in oil mass, obtain enter core wafer in oil mass O1；

The water L1 entered in core wafer (4) in step (2) is subtracted in the buret of step (3) middle outlet end (B) connection Water obtains the water L2 after saturated oils in core wafer (4)；

The pressure break liquid measure for the buret for containing fracturing fluid when by step (4) fracturing fluid displacement of reservoir oil goes out after subtracting the pressure break displacement of reservoir oil The water in buret that mouth end (B) connects is detained along with the water L2 after saturated oils in core wafer (4) Pressure break liquid measure F1 in core wafer (4)；

The oil mass O1 entered in core wafer in step (3) subtracts the oil mass of the buret of step (4) middle outlet end (B) connection, Obtain the oil mass O2 after the fracturing fluid displacement of reservoir oil in core wafer (4)；

The oil mass in buret that outlet end (B) is connected when instead driving fracturing fluid by step (5) oil subtracts oily anti-drive fracturing fluid After oil mass in the buret that connects of arrival end (A), along with the oil mass O2 in core wafer (4) after step (4), Obtain the oily anti-interior oil mass O3 of core wafer (4) after driving fracturing fluid；

Pressure break liquid measure F1 after step (4) into core wafer (4) subtracts the buret of arrival end A connection in step (5) In pressure break liquid measure, obtain the oily anti-pressure break liquid measure F2 driven after fracturing fluid in core wafer (4), then the spontaneous imbibition rock of fracturing fluid Heart remnants fracturing fluid percentage is

6. a kind of spontaneous imbibition research method of visualization fracturing fluid according to claim 4, which is characterized in that the step (1) in, the water filled in the first buret (3) is the sample prepared according to target zone stratum aqueous nature, and methyl blue, which is added, in water makes It is blue；

In the step (4), fracturing fluid is the sample that hydraulic fracturing construction pressure break formula of liquid is prepared, and methyl blue is added in fracturing fluid It is allowed to blue；

In the step (5), the oil uses kerosene, and oil red dyeing is added in kerosene and is allowed to take on a red color.

7. a kind of spontaneous imbibition research method of visualization fracturing fluid according to claim 6, which is characterized in that the step (6) in, the process for calculating the spontaneous imbibition rock core remnants fracturing fluid percentage of fracturing fluid is as follows:

Step 6.1, terminate since vacuumizing step (1) to the anti-fracturing fluid that drives of step (5) oil, shot by optical microscopy 6 Step (1) core wafer (4) into step (5) operating process, and shoot complete after step (2) to step (5) each the end of the step The image of shooting is sent to electronic computer (7) by the ken, optical microscopy (6)；

Step 6.2, electronic computer (7) portrays the grease color in image by different threshold values, obtains the full ken The chromatogram of image；

Step 6.3, electronic computer (7) analyzes residual amount according to chromatogram, obtains step (4) fracturing fluid displacement of reservoir oil The blue colored area F of journey₁', with the anti-blue colored area F for driving fracturing fluid process of step (5) oil₂', and calculate the spontaneous imbibition rock of fracturing fluid Heart remnants fracturing fluid percentage is

8. a kind of spontaneous imbibition research method of visualization fracturing fluid, feature according to claim 4-7 any one exist In in the step (1), the time vacuumized is 5~10 hours；

In the step (2), the time of the rock core saturated water of core wafer (4) is 2~3 hours；

In the step (3), force (forcing) pump (1) is 5~8 hours to the buret pressing time containing oil；

In the step (4), force (forcing) pump (1) is 5~8 hours to the buret pressing time containing fracturing fluid；

In the step (5), buret pressing time of the force (forcing) pump (1) containing oil is 5~8 hours.

9. a kind of spontaneous imbibition research method of visualization fracturing fluid, feature according to claim 4-7 any one exist In in the step (3), force (forcing) pump (1) is 0.02~0.20MPa to the pressure of the buret pressurization containing oil；

In the step (4), force (forcing) pump (1) is 0.02~0.20MPa to the pressure of the buret pressurization containing fracturing fluid；

In the step (5), force (forcing) pump (1) is 0.02~0.20MPa to the pressure of the buret pressurization containing oil.

10. a kind of spontaneous imbibition research method of visualization fracturing fluid, feature according to claim 4-7 any one exist In, from step (3) to step (5), after each step, by core wafer (4) place 6~12 hours, make core wafer (4) Aging.