CN103470233A - A natural gas huff and puff oil recovery process system and oil recovery method for heavy oil reservoirs - Google Patents

Abstract

A heavy oil reservoir natural gas huff-puff oil production process system and an oil production method. The method comprises the following steps: drilling a well in a target region of an oil reservoir, drilling a stratum, an oil layer, an interlayer and a natural gas layer from top to bottom, communicating the oil layer with the gas layer through a shaft, and perforating the oil layer and the gas layer; selecting the length of an eye tube, and installing a flow meter, a pressure gauge and a flow control valve; a production pipe column and a cable are put in, the production pipe column is sequentially connected with a first oil pipe, an oil well pump, an eye tube, a packer and a second oil pipe in series, and the cable conducts signals; setting a packer; installing a Christmas tree and an oil pumping unit; closing the well, and opening the flow control valve to enable the natural gas to flow into the oil layer; closing the flow control valve, and then stewing; and after the designed soaking time is reached, opening the well to recover oil. The natural gas layer high-pressure energy is fully utilized, so that the natural gas directly flows into the heavy oil layer from the gas layer through the shaft, the problems of complex process flow, high operation cost and high energy consumption are solved, the natural gas huff and puff efficiency is high, and the oil extraction efficiency is greatly improved.

Description

A natural gas huff and puff oil recovery process system and oil recovery method for heavy oil reservoirs

technical field

The invention relates to the technical field of petroleum exploitation, in particular to a natural gas huff and puff oil recovery process system and oil recovery method for heavy oil reservoirs.

Background technique

At present, heavy oil reservoirs are often exploited by methods such as steam injection huff and puff, SAGD, natural gas injection huff and puff, burning oil layers, and lifting with dilution on pumps. Among them, the oil recovery method of natural gas injection huff and puff is mainly to extract the natural gas in the gas layer on the ground to obtain the natural gas source, and then use the compressor to inject the natural gas into the oil layer through the oil well (gas swallowing process), and the natural gas dissolves into the crude oil to reduce the viscosity of the crude oil , and then, open the oil well to produce crude oil and natural gas dissolved in crude oil together (breathing process).

The Tuyuke heavy oil reservoir is the first oilfield in China to conduct a natural gas throughput test. In the test stage, liquefied natural gas (LNG) was used as the gas source, and the following injection process was adopted: the liquefied natural gas in the LNG storage tank was boosted to the inlet of the compressor through a low-temperature liquid booster pump, vaporized by the LNG vaporizer, and then entered into the buffer tank at the inlet of the compressor After the compressor is pressurized, it enters the gas distribution valve group for metering and distributes it to the injection wellhead. The specific gas injection process is: LNG storage tank → low temperature liquid booster pump → vaporizer → compressor inlet buffer tank → gas injection compressor → gas distribution valve group → (via single well pipeline) gas injection well (Yin Baishou, Li Jun, heavy oil Surface Technology of Natural Gas Huff and Puff Test, Oil and Gas Field Surface Engineering Vol. 26 No. 10, 2007: 24). At present, Tuyuke Oilfield and Lukeqin Oilfield have implemented the integrated technology of natural gas huff and puff injection and production, which needs to meet the following requirements: (1) optimize the well completion and cementing methods, in order to meet the performance requirements of gas injection huff and puff gas sealing, prevent Gas channeling occurs during the gas injection process to ensure the safety of gas injection. For the horizontal well vertical section and the oil layer of the vertical well, the long cement cement section and the vertical well section are used to complete the well; , which can realize air sealing under high pressure; during the injection process, the pump should be lifted out of the pump seat and suspended on the wellhead to ensure the safe injection of natural gas from the tubing; the wellhead is within a certain height, which can meet the oil production requirements of the rod pump; air-sealing wellhead and supporting tools It mainly includes polished rod connectors, high-pressure gas-sealed wellheads, standard casing heads, polished rod sealers, etc.; (3) In view of the requirements for the gas-tightness of the pipe string during the natural gas huff-puff gas injection process, the high-pressure gas sealing performance and Production safety and reliability, design of gas injection huff and puff gas injection and oil production integrated string; (4) In order to meet the requirements of both gas injection and production, the injection-production switching process is designed (for specific devices, please refer to the following articles: Gong Xiaoxiong, Wang Aihua, Li Jun et al., Research and Application of Injection-production Integrated Technology for Deep Heavy Oil Natural Gas Huff-puff, Journal of Petroleum and Natural Gas, Vol. 30, No. 1, 2008: 303-305; , Vol. 36 No. 8, 2008: 74-77).

The above-mentioned technologies have extremely high requirements for well completion and cementing methods, wellheads and supporting tools, oil production strings and injection-production switching processes. The processes and operating procedures are very complicated, costly, and consume a lot of energy.

Contents of the invention

In view of the defects described in the background technology, the purpose of the present invention is to provide a natural gas huff and puff oil recovery process system and oil recovery method for heavy oil reservoirs, which can make full use of the high-pressure energy of the natural gas layer to directly flow the natural gas from the gas layer through the wellbore The oil layer avoids the problems of complex process flow, high operation cost and high energy consumption.

Above-mentioned purpose of the present invention is achieved by the following technical solutions:

First of all, it should be explained that in the actual production and operation process, the pumping unit, christmas tree, pump hanging device, oil well pump, sucker rod, tailpipe, screen pipe and other devices required for conventional heavy oil exploitation are all matched with the present invention. Because the structure, function, installation method and use method of these devices have been popularized, the present invention no longer repeats the structure, function, installation method and use method of the above-mentioned devices one by one.

The invention provides a natural gas huff and puff production process system for heavy oil reservoirs. A production string is lowered into the wellbore, and the production string is connected in series from top to bottom with a first oil pipe, an oil pump, an eye pipe, and a packer. The wellbore has a perforation section at the position corresponding to the oil layer and the natural gas layer; the setting position of the packer is between the oil layer and the natural gas layer, so as to seal the oil layer between the oil layer and the natural gas layer. The ring is empty.

In the heavy oil reservoir natural gas huff and puff production process system described above, the second oil pipe is provided with a flowmeter for monitoring the flow of natural gas and a pressure gauge for monitoring the pressure of natural gas; flow control valve.

The natural gas huff and puff production process system for heavy oil reservoirs as described above is characterized in that the flowmeter is connected to the flowmeter terminal at the ground end through the first cable, and the flowmeter terminal displays the flow value; the pressure gauge is connected through the second cable It is connected to the pressure gauge terminal on the ground side, and the pressure gauge terminal displays the pressure value; the flow control valve is connected to the flow control valve terminal on the ground side through a third cable, and the valve size of the flow control valve is adjusted through the flow control valve terminal to control natural gas flow rate; the oil production process system is also equipped with a Christmas tree at the wellhead, and the first cable hole, the second cable hole and the third cable hole are arranged on the said oil production tree, so that the first cable, the second cable and the third cable are respectively Correspondingly pass through; the gap between the cable hole and the cable is sealed by a rubber gasket.

The natural gas stimulation and puff production process system for heavy oil reservoirs as described above is characterized in that the first cable extends from the flowmeter terminal, passes through the first cable hole on the Christmas tree, and extends into the oil collar along the wellhead empty, then enter the inside of the eye pipe through the hole of the eye pipe and extend down to the second oil pipe, and connect with the flow meter located in the second oil pipe; the second cable protrudes from the end of the pressure gauge and passes through the oil tree The second cable hole on the top extends along the wellhead into the casing annulus, and then enters the inside of the eye pipe through the hole of the eye pipe and extends downward to the second oil pipe to connect with the pressure gauge located in the second oil pipe; the third The cable protrudes from the terminal of the flow control valve, passes through the third cable hole on the Christmas tree, extends along the wellhead into the oil casing annulus, and then enters the inside of the eye pipe through the hole of the eye pipe and extends downward to the second oil pipe, It is connected with the flow control valve connected in series at the end of the second oil pipe.

The present invention also provides a natural gas huff and puff recovery method for heavy oil reservoirs, comprising:

Step A: Drill oil wells in the target area of the reservoir, drill through formations, oil layers, interlayers and natural gas layers from top to bottom, connect the oil layers and gas layers through the wellbore, and perforate the wellbore sections corresponding to the oil layers and natural gas layers;

Step B: Select an eye pipe of appropriate length according to the material strength of the eye pipe, the production capacity of the natural gas layer and the thickness of the interlayer; set a flowmeter for monitoring the flow of natural gas and a pressure gauge for monitoring the pressure of natural gas in a second oil pipe, A flow control valve for controlling the flow of natural gas is installed at the end of the second oil pipe, and the cables of the flow meter, pressure gauge and flow control valve are respectively passed through the holes on the second oil pipe and the eye pipe, and the reserved length of each cable is Slightly greater than the depth of the wellbore;

Step C: Connect the first tubing, oil well pump, borehole, packer and second tubing in sequence to form a production string, run the production string in the wellbore, and simultaneously run the first cable, the second cable and The third cable, and set the packer to the position between the corresponding oil layer and the natural gas layer in the wellbore; respectively pass the free ends of the first cable, the second cable and the third cable through the first cable on the Christmas tree The hole, the second cable hole and the third cable hole are respectively connected to the terminal of the flow meter, the terminal of the pressure gauge and the terminal of the flow control valve; install conventional wellhead devices such as Christmas trees and pumping units;

Step D: Close the nozzles on the pumping unit and the Christmas tree to shut down the well, open the valve of the flow control valve, and let the natural gas flow into the oil layer through the second tubing section, the eye pipe, and the casing annulus;

Step E: close the valve of the flow control valve, and then stew the well;

Step F: After reaching the designed soaking time, keep the valve of the flow control valve closed, open the pumping unit and oil nozzle, and open the well for oil production.

The above-mentioned method, wherein: in the step E, when the injection amount of natural gas monitored by the flow meter reaches a predetermined value, the valve of the flow control valve is then closed.

The above-mentioned method, wherein: in the oil recovery process of step F, when the crude oil output fails to reach the design target, repeat the steps D to F.

The above-mentioned method also includes the following steps between step C and step D:

Step C': firstly close the valve of the flow control valve, open the pumping unit and oil nozzle to extract oil until the oil output is lower than the design production capacity, and then proceed to the step D.

By virtue of the above technical solutions, the features and advantages of the present invention are:

The oil recovery process system and the oil recovery method proposed by the invention are especially suitable for the situation where a large-scale abnormally high-pressure natural gas layer is developed in the lower part of the heavy oil layer. For natural gas layers with non-abnormal high pressure or small scale and low production capacity, the pressure difference between the natural gas layer and the heavy oil layer is not large enough, and the energy of the natural gas layer is low. The pressure of the heavy oil layer will gradually decrease, and when the pressure difference between the natural gas layer and the oil layer reaches a certain value, the oil recovery process system and oil recovery method proposed by the present invention can be used.

The invention connects the natural gas layer and the oil layer through the wellbore, makes full use of the pressure difference between the natural gas layer and the oil layer, induces natural gas to flow into the oil layer automatically, reduces the viscosity of crude oil, and realizes natural gas huff and puff oil production without special well completion and cementing methods, Wellhead equipment, production string and injection-production switching process. Therefore, on the basis of improving crude oil output and recovery factor, the present invention has many advantages, such as simple technological process, low oil recovery operation cost, low energy consumption, etc., and improves the economic benefits of the oil field.

Description of drawings

Fig. 1 is the schematic diagram of the present invention in the gas swallowing process;

Fig. 2 is a schematic diagram of the present invention during exhalation.

Detailed ways

In order to disclose the purpose, technical means and technical effects of the present invention more completely and clearly, the following is a detailed description, and please refer to the accompanying drawings and component numbers.

Please refer to Fig. 1, at first introduce the oil production process system of the present invention.

A natural gas huff and puff production process system for heavy oil reservoirs. A set of production string 1 is lowered into the wellbore 5. The production string 1 is sequentially connected with a first oil pipe 7, an oil well pump 20, and an eye pipe from top to bottom. 9. The packer 17 and the second tubing 12; the wellbore 5 has perforation sections at the positions corresponding to the oil layer 8 and the natural gas layer 13, and each perforation section has a plurality of blastholes 19 (or 14); The length of 9 is determined by the material strength of the eye pipe 9, the productivity of the natural gas layer 13, and the thickness of the interlayer 10; The oil casing annulus 18 between 13 (referring to the annulus between the production string 1 and the casing 28), and the position of the packer 17 should be as close as possible to the natural gas layer 13 under the condition that the strength of the eye pipe 9 allows , to ensure that the eye pipe 9 has a sufficient length, that is, there are enough holes 90, so as to provide as many circulation channels as possible for the natural gas.

The second oil pipe 12 is provided with a flow meter 11 for monitoring the flow of natural gas and a pressure gauge 16 for monitoring the pressure of natural gas; the end of the second oil pipe 12 is provided with a flow control valve 15 for controlling the flow of natural gas.

Preferably, the flowmeter 11 is connected with the flowmeter terminal 26 at the ground end through the first cable 21, and the flowmeter terminal 26 displays the flow value; the pressure gauge 16 is connected with the pressure gauge terminal 25 at the ground end through the second cable 22 connection, the pressure gauge terminal 25 displays the pressure value; the flow control valve 15 is connected to the flow control valve terminal 2 at the ground end through the third cable 6, and the valve size of the flow control valve 15 is adjusted through the flow control valve terminal 2 to control the natural gas flow rate; the oil production process system is also equipped with a Christmas tree 29 at the wellhead, and the first cable hole 31, the second cable hole 32 and the third cable hole 30 are arranged on the said oil production tree, so that the first cable 21, the second cable 22 and the third cable 6 pass through respectively; the gap between the cable hole and the cable is sealed by a rubber pad.

Preferably, the first cable 21 extends from the flowmeter terminal 26, passes through the first cable hole 31 on the Christmas tree 29, extends along the wellhead 24 into the oil casing annulus 18, and then passes through the hole of the eye pipe 9. The hole 90 enters the inside of the eye pipe 9 and extends downward to the second oil pipe 12, and is connected with the flowmeter 11 located in the second oil pipe 12; the second cable 22 protrudes from the pressure gauge terminal 25 and passes through the oil tree The second cable hole 32 on 29 extends into the oil casing annulus 18 along the wellhead 24, and then enters the inside of the eye pipe 9 through the hole 90 of the eye pipe 9 and extends downward to the second oil pipe 12, and is located in the second oil pipe 12 connected to the pressure gauge 16; the third cable 6 extends from the flow control valve terminal 2, passes through the third cable hole 30 on the Christmas tree 29, extends along the wellhead 24 into the oil casing annulus 18, and then passes through the eye The hole 90 of the pipe 9 enters the inside of the eye pipe 9 and extends downward to the second oil pipe 12 , and is connected with the flow control valve 15 connected in series at the end of the second oil pipe 12 .

Please refer to Figure 1 and Figure 2 together. The oil recovery method of natural gas huff and puff in heavy oil reservoirs will be introduced below. The method includes:

Step A: drill an oil well 3 in the target area of the reservoir, drill through the stratum 4, the oil layer 8, the interlayer 10 and the natural gas layer 13 from top to bottom, connect the oil layer 8 and the natural gas layer 13 through the wellbore 5, and correspond to the oil layer 8 and the natural gas layer Perforating the wellbore section of the natural gas layer 13;

Step B: Select an eye pipe 9 of appropriate length according to the material strength of the eye pipe, the production capacity of the natural gas layer 13 and the thickness of the interlayer 10; a flow meter 11 for monitoring the flow of natural gas and a flow meter for monitoring the pressure of natural gas are arranged in the second oil pipe 12 Pressure gauge 16, the flow control valve 15 that is used to control the flow of natural gas is arranged at the end of the second oil pipe 12, and the cables of flow meter 11, pressure gauge 16 and flow control valve 15 are respectively passed through the second oil pipe 12 and the eye pipe 9. Eyelet 90, and make the length of each cable slightly greater than the depth of shaft 5;

Step C: Connect the first tubing 7, the oil well pump 20, the borehole 9, the packer 17 and the second tubing 12 in order to form a production tubing string 1, run the production tubing string 1 into the wellbore 5, and simultaneously run Insert the first cable 21, the second cable 22 and the third cable 6, and set the packer 17 to the position between the corresponding oil layer 8 and the natural gas layer 13 in the wellbore 5; insert the first cable 21, the second cable 22 and the The free end of the third cable 6 passes through the first cable hole 31, the second cable hole 32 and the third cable hole 30 on the Christmas tree 29 respectively, and then connects with the flowmeter terminal 26, the pressure gauge terminal 25 and the flow control valve terminal respectively. 2 phase connection; installation of conventional wellhead devices such as Christmas tree 29 and pumping unit;

Step D: close the oil nozzle 27 on the pumping unit and the Christmas tree 29 to close the well, open the valve of the flow control valve 15, and let the natural gas flow into the oil layer 8 through the second oil pipe section 12, the eye pipe 9, and the oil casing annulus 18. The flow direction of natural gas is shown by the arrow in Figure 1;

Step E: close the valve of the flow control valve 15, then stew the well;

Step F: After reaching the designed soaking time, keep the valve of the flow control valve 15 closed, open the pumping unit and the oil nozzle 27, and open the well for oil production. At this time, the flow of crude oil is shown by the arrow in Figure 2.

In the step E, when the injection amount of natural gas monitored by the flow meter 11 reaches a predetermined value, the valve of the flow control valve 15 is closed. The pre-determined value of natural gas injection rate is demonstrated in advance by methods such as reservoir engineering and numerical simulation.

Preferably, during the oil recovery process in step F, when the crude oil output fails to reach the design target, repeat steps D to F. Crude oil production is a dynamic process. With the extraction of crude oil, the thinner oil will be extracted first, while the thicker oil will remain in the oil layer and gradually accumulate, resulting in a decrease in production. Once the crude oil output is lower than the design value, the natural gas stimulation and puff oil recovery method of the present invention can be started to dissolve the natural gas into the oil layer to dilute the heavy oil, so as to facilitate the normal output of crude oil.

Preferably, the following steps are also included between step C and step D:

Step C': first close the valve of the flow control valve 15, open the pumping unit and the oil nozzle 27 to extract oil until the oil output is lower than the design capacity, and then proceed to the step D. This step shows that in the early stage of production when natural gas throughput is not required, oil recovery operations can be carried out as usual until the oil recovery does not meet the requirements before starting natural gas throughput.

The premise or applicable condition of the present invention is that the converted pressure of the natural gas layer (referring to the residual pressure at the position where the natural gas reaches the oil layer through the wellbore after being produced from the natural gas layer) is far greater than the pressure of the oil layer, and the natural gas layer has large reserves and high production capacity; natural gas The larger the pressure difference between the oil layer and the gas layer, the easier the gas swallowing process will be.

If the converted pressure of the natural gas layer is slightly higher than, approximately equal to, or slightly lower than the pressure of the oil layer, or the reserves of the natural gas layer are small and the production capacity is low, and the natural gas layer does not have enough energy to inject a large amount of natural gas into the oil layer, then it should be divided into the following two Two situations: 1. For heavy oil reservoirs with low crude oil viscosity, if the oil well can reach the designed production capacity, the above step C' can be directly carried out for production; 2. For heavy oil reservoirs with very high crude oil viscosity, if the oil well cannot To reach the designed production capacity, measures must be taken first, such as wellbore heating, etc., to reduce the viscosity of the heavy oil to a certain extent before proceeding to the above step C' for production. With the exploitation of the oil layer, the pressure of the oil layer gradually decreases, and the production capacity decreases, while the pressure difference between the natural gas layer and the oil layer will gradually increase. When the pressure difference between the natural gas layer and the oil layer reaches a certain value (through reservoir engineering methods and When the numerical simulation method is demonstrated), the above step D can be carried out to carry out the natural gas swallowing process.

The above are only some illustrative embodiments of the present invention, and are not intended to limit the scope of the present invention. Anyone skilled in the art can make equivalent changes and modifications without departing from the concept and principles of the present invention. should be included within the scope of protection of this patent.

Claims (8)

1. A natural gas huff and puff production process system for heavy oil reservoirs, characterized in that a production string is lowered in the wellbore, and the production string is sequentially connected in series with a first oil pipe, an oil well pump, and an eye pipe from top to bottom , a packer, and a second tubing; the wellbore has a perforation section at the position corresponding to the oil layer and the natural gas layer; the setting position of the packer is between the oil layer and the natural gas layer to seal off the The oil jacket annulus between. 2. The heavy oil reservoir natural gas huff and puff recovery process system according to claim 1, characterized in that, the second oil pipe is provided with a flowmeter for monitoring the flow of natural gas and a pressure gauge for monitoring the pressure of natural gas; The end of the oil pipe is provided with a flow control valve for controlling the flow of natural gas into the oil pipe. 3. The heavy oil reservoir natural gas huff and puff recovery process system according to claim 2, wherein the flowmeter is connected with the flowmeter terminal positioned at the ground end through the first cable, and the flowmeter terminal displays the flow value; the pressure The gauge is connected to the pressure gauge terminal on the ground side through the second cable, and the pressure gauge terminal displays the pressure value; the flow control valve is connected to the flow control valve terminal on the ground side through the third cable, and the flow control valve is adjusted through the flow control valve terminal. size, to control the flow of natural gas; the oil production process system is also equipped with a Christmas tree at the wellhead, and the first cable hole, the second cable hole and the third cable hole are arranged on the said oil production tree, so that the first cable, the second cable and the third cable pass through respectively; the gap between the cable hole and the cable is sealed by a rubber pad. 4. The heavy oil reservoir natural gas huff and puff production process system according to claim 3, characterized in that, the first cable extends from the flowmeter terminal, passes through the first cable hole on the Christmas tree, and runs along the wellhead. Extending into the annulus of the oil jacket, and then entering the interior of the eye pipe through the hole of the eye pipe and extending down to the second oil pipe, and connected with the flow meter located in the second oil pipe; the second cable extends from the end of the pressure gauge , pass through the second cable hole on the Christmas tree, extend along the wellhead into the oil casing annulus, enter the inside of the eye pipe through the hole of the eye pipe and extend down to the second oil pipe, and connect with the pressure gauge located in the second oil pipe The third cable extends from the terminal of the flow control valve, passes through the third cable hole on the Christmas tree, extends along the wellhead into the oil casing annulus, and then enters the inside of the eye pipe through the hole of the eye pipe and extends downward To the second oil pipe, connected with the flow control valve connected in series at the end of the second oil pipe. 5. A natural gas huff and puff recovery method for heavy oil reservoirs, comprising: Step A: Drill oil wells in the target area of the reservoir, drill through formations, oil layers, interlayers and natural gas layers from top to bottom, connect the oil layers and gas layers through the wellbore, and perforate the wellbore sections corresponding to the oil layers and natural gas layers; Step B: Select an eye pipe of appropriate length according to the material strength of the eye pipe, the production capacity of the natural gas layer and the thickness of the interlayer; set a flowmeter for monitoring the flow of natural gas and a pressure gauge for monitoring the pressure of natural gas in a second oil pipe, A flow control valve for controlling the flow of natural gas is installed at the end of the second oil pipe, and the cables of the flow meter, pressure gauge and flow control valve are respectively passed through the holes on the second oil pipe and the eye pipe, and the reserved length of each cable is Slightly greater than the depth of the wellbore; Step C: Connect the first tubing, oil well pump, borehole, packer and second tubing in sequence to form a production string, run the production string in the wellbore, and simultaneously run the first cable, the second cable and the third cable, and set the packer to the position between the corresponding oil layer and the natural gas layer in the wellbore; pass the free ends of the first cable, the second cable and the third cable through the first cable hole, The second cable hole and the third cable hole are respectively connected to the terminal of the flow meter, the terminal of the pressure gauge and the terminal of the flow control valve; install the Christmas tree and the pumping unit; Step D: Close the nozzles on the pumping unit and the Christmas tree to shut down the well, open the valve of the flow control valve, and let the natural gas flow into the oil layer through the second tubing section, the eye pipe, and the casing annulus; Step E: close the valve of the flow control valve, and then stew the well; Step F: After reaching the designed soaking time, keep the valve of the flow control valve closed, open the pumping unit and oil nozzle, and open the well for oil production. 6. The method of claim 5, wherein: In the step E, when the injection amount of natural gas monitored by the flow meter reaches a predetermined value, the valve of the flow control valve is closed. 7. A method according to claim 5 or 6, wherein: During the oil recovery process in step F, when the crude oil output fails to reach the design target, repeat steps D to F. 8. The method according to claim 5 or 6, further comprising the steps between step C and step D: Step C': firstly close the valve of the flow control valve, open the pumping unit and oil nozzle to extract oil until the oil output is lower than the design production capacity, and then proceed to the step D.

Images