CN-116593641-B - Experimental device and method for simulating hydrate secondary formation

CN116593641BCN 116593641 BCN116593641 BCN 116593641BCN-116593641-B

Abstract

The invention is suitable for the technical field of hydrate simulated exploitation, and provides an experimental device and a method for simulating hydrate secondary formation, wherein the device comprises a reaction unit, a gas injection unit, a liquid injection unit, a temperature control unit, a vacuum degree control unit, an outlet control unit, a gas circulation unit and a data monitoring and processing unit; the reaction unit comprises a reaction kettle, a vacuum box and a constant-temperature water bath box, wherein the reaction kettle is arranged in the vacuum box, and the vacuum box and the reaction kettle in the vacuum box are arranged in the constant-temperature water bath box. According to the invention, through the arranged reaction kettle, the convergence flow effect of gradually reducing the seepage radius of the hydrate decomposition product in the near-well region radial seepage process is simulated, the rule of secondary formation of the near-well region hydrate in the exploitation process is explored, and a feasible scheme and technical guidance are provided for preventing and controlling the secondary hydrate in the natural gas hydrate exploitation process.

Inventors

LI BING
Shan Hengfeng
ZHANG GUOBIAO
JIANG SHUHUI
JIANG BING
LIU YIZHUO
LI XIANG
WU ZIYAN
ZHANG JIAQIAO

Assignees

中国地质大学（北京）

Dates

Publication Date: 20260512
Application Date: 20230417

Claims (10)

1. The experimental device for simulating the secondary formation of the hydrate comprises a reaction unit, a gas injection unit, a liquid injection unit, a temperature control unit, a vacuum degree control unit, an outlet control unit, a gas circulation unit and a data monitoring and processing unit, and is characterized in that, The reaction unit comprises a reaction kettle, a vacuum box and a constant-temperature water bath box, wherein the reaction kettle is arranged in the vacuum box, and the vacuum box and the reaction kettle in the vacuum box are arranged in the constant-temperature water bath box; The reaction kettle comprises more than two sections of single-section reaction kettles which are cascaded, wherein the inner diameter shrinkage of the more than two sections of single-section reaction kettles is determined based on a similar principle so as to simulate the convergence flow effect that the seepage radius of a hydrate decomposition product is gradually reduced in the near-well region radial seepage process; the gas injection unit is used for injecting gas into the reaction kettle to simulate the gas generated by decomposing the hydrate; the liquid injection unit is used for injecting liquid into the reaction kettle to simulate the liquid generated by decomposing the hydrate; The temperature control unit is used for controlling the temperature in the constant-temperature water bath box; The vacuum degree control unit is used for controlling the vacuum degree in the vacuum box; The outlet control unit is used for controlling the outlet pressure of the reaction kettle and separating and metering gas and liquid generated by experiments; the gas circulation unit is used for conveying the gas separated by the outlet control unit to the gas injection unit again so as to realize the recycling of the gas; the data monitoring and processing unit is used for monitoring and collecting physical parameters in the reaction kettle in the experimental process, wherein the physical parameters at least comprise temperature, pressure and resistivity.
2. The experimental device for simulating hydrate secondary formation according to claim 1, wherein any two adjacent single-stage reaction kettles are connected through a reducing flange; The outer end face of the single-section reaction kettle at the outermost end is hermetically arranged through a flange, and an injection port and an outlet are respectively arranged on the flange so as to realize injection and output of gas and liquid; each section of the single-section reaction kettle is reserved with a high-pressure connector for connecting the data monitoring and processing unit, and the pressure-resistant range between the single-section reaction kettle and the flange is 0-35MPa.
3. The experimental apparatus for simulating hydrate secondary formation according to claim 1, wherein the constant temperature water bath is filled with a first medium which passes over the top of the vacuum box; the temperature control unit comprises a first booster pump, a low-temperature constant-temperature tank and a second booster pump, wherein a cooling medium is arranged in the low-temperature constant-temperature tank, and the first medium in the constant-temperature water bath circularly flows in a closed loop route formed by the constant-temperature water bath, the first booster pump, the low-temperature constant-temperature tank, the second booster pump and the constant-temperature water bath; the first medium in the constant-temperature water bath box is in indirect contact with the cooling medium in the low-temperature constant-temperature tank, so that heat exchange is carried out, and the temperature of the reaction kettle is maintained at a preset temperature.
4. The experimental device for simulating hydrate secondary formation according to claim 1, wherein the gas injection unit comprises a gas cylinder, a first regulating valve group and a gas flow controller, the gas cylinder, the first regulating valve group, the gas flow controller, the vacuum box and the reaction kettle are sequentially communicated through a gas pipeline, methane gas is stored in the gas cylinder, and flows through the first regulating valve group, the gas flow controller and the vacuum box in sequence and is injected into the reaction kettle, wherein the first regulating valve group is used for controlling the pressure of the gas, and the gas flow controller is used for controlling the flow of the gas; the liquid injection unit comprises a liquid storage tank, a constant-pressure constant-flow pump and a second regulating valve group which are cascaded, wherein water is stored in the liquid storage tank, and the constant-pressure constant-flow pump injects the water in the liquid storage tank into a gas pipeline at a constant flow through the second regulating valve group, and then the water is mixed with gas and then injected into the reaction kettle.
5. The experimental device for simulating secondary formation of hydrate according to claim 1, wherein the vacuum box comprises a box body, an end cover, supporting pieces and a heat insulation plate, sealing is achieved between the end cover and the box body through bolts and plastic sealing gaskets, the heat insulation plate is laid on the inner bottom surface of the box body, and a plurality of supporting pieces are arranged on the heat insulation plate and used for fixing a reaction kettle and suspending the reaction kettle in the box body.
6. The apparatus according to claim 5, wherein the vacuum degree control unit comprises a vacuum gauge, a third regulating valve group and a vacuum pump, the vacuum gauge and the third regulating valve group are installed on the case, and the vacuum pump is used for evacuating the vacuum case.
7. The experimental apparatus for simulating hydrate secondary formation according to claim 1, wherein the data monitoring processing unit includes a temperature sensor, a pressure sensor, a resistivity sensor, a data acquisition module, and a data processing module; The temperature sensors and the pressure sensors are uniformly distributed along the axial direction of the reaction kettle and are oppositely arranged along the axis of the reaction kettle, so as to quantitatively monitor the temperature and pressure changes caused by the throttling expansion effect and the secondary hydrate generation in the experimental process; the resistivity sensor comprises paired resistivity probes, and each pair of resistivity probes is uniformly distributed along the axial direction of the reaction kettle and is oppositely arranged along the axis of the reaction kettle so as to qualitatively monitor the resistivity change caused by the formation of secondary hydrate; the data acquisition module is used for processing signals acquired by the temperature sensor, the pressure sensor and the resistivity sensor and transmitting the acquired signals to the data processing module.
8. The experimental apparatus for simulating hydrate secondary formation according to claim 1, wherein the outlet control unit comprises a fourth valve block installed at an end cap of the vacuum box and communicating with an outlet of the reaction vessel through a section of high pressure line for controlling an outlet pressure of the reaction vessel to simulate a pressure of the production well during hydrate exploitation, and a flow meter for monitoring a gas flow rate at the outlet of the reaction vessel.
9. The experimental device for simulating hydrate secondary formation according to claim 1, wherein the gas circulation unit comprises a gas-liquid separator, a balance measurer, a first gas tank, a third booster pump, and a second gas tank; The gas-liquid separator is used for separating a product output by an outlet of the reaction kettle, the balance measurer is positioned at the outlet end of the gas-liquid separator and is used for measuring the weight of separated liquid, the first gas storage tank is used for collecting the separated gas, and the third booster pump is used for pumping the collected gas to the second gas storage tank after pressurizing so as to re-convey the gas in the second gas storage tank to the gas injection unit or the reaction kettle to realize gas circulation.
10. An experimental method for simulating the secondary formation of a hydrate using the experimental apparatus for simulating the secondary formation of a hydrate according to any one of claims 1 to 9, the method comprising the steps of: Preparing a sediment sample in situ in each section of single-section reaction kettle by using a simulated medium mixed with distilled water in a layering compaction method before a purging experiment, connecting each section of single-section reaction kettle and a corresponding data monitoring and processing unit, transferring the reaction kettle into a vacuum box, connecting and fixing the corresponding part of the reaction kettle with the vacuum box, sealing the vacuum box, checking the air tightness of the reaction kettle and the vacuum box, and ensuring good air tightness for the next experiment; Pre-purging experiment, namely pre-purging the reaction kettle by using methane gas, weighing collected water and calculating residual water saturation of sediment samples in the reaction kettle after observing that the outlet end of the reaction kettle is no longer water-out; The method comprises the steps of firstly forming and decomposing hydrate, namely reducing the temperature of a constant-temperature water bath to a first temperature, opening an outlet end of a reaction kettle to decompose the hydrate after the hydrate is completely formed, adjusting the temperature of the constant-temperature water bath to a second temperature after the hydrate is completely decomposed, carrying out vacuumizing treatment after the second temperature is stable, and starting a purging experiment after the vacuum degree reaches 100%; And in the purging experiment process, monitoring the temperature, pressure and resistivity changes of different positions of the reaction kettle in real time, comprehensively judging the secondary generation of the hydrate and the position of the secondary generation by using the monitoring data, and analyzing the saturation change of the secondary hydrate by combining the flow change.

Description

Experimental device and method for simulating hydrate secondary formation Technical Field The invention belongs to the technical field of simulated exploitation of hydrates, and particularly discloses an experimental device and method for simulating secondary formation of hydrates. Background The natural gas hydrate in the hydrate has become an important potential efficient clean oil gas succession energy source internationally recognized by virtue of the advantages of abundant reserves, cleanness, no pollution, high energy density and the like. In the hydrate depressurization exploitation process, hydrate decomposition products, namely methane and water, generated in a hydrate decomposition zone continuously reduce temperature due to throttling expansion effect in the seepage process to a production well, hydrate can be regenerated in a near well zone where the hydrate is completely decomposed, a gas production channel is blocked, and gas production efficiency is affected. The space-time evolution process of the secondary hydrate relates to the coupling problem of multiple physical fields such as a temperature field, a pressure field, an ion concentration field and the like and multiple physical factors such as gas-liquid seepage and phase change, and the research of the law of the coupling problem has important significance for realizing the industrialized development of the hydrate in the future. However, most of the existing experimental devices for researching the secondary hydrate are one-dimensional and small-scale experimental devices, the convergent flow effect that the fluid seepage area is gradually reduced in the actual exploitation process is not considered, the heat exchange between the reaction kettle and the constant temperature medium is not considered, the influence of the convergent flow effect and the throttling expansion effect on the secondary formation of the near-well region hydrate in the non-convective heat exchange environment cannot be simulated, and improvement is needed. Disclosure of Invention The embodiment of the invention aims to provide an experimental device and method for simulating hydrate secondary formation, which aim to solve the defects that the existing experimental device cannot simulate the influence of a convergence flow effect and a throttling expansion effect on the secondary formation of near-well region hydrate in a non-convection heat exchange environment, explore the rule of hydrate secondary formation in the exploitation process, clear the mechanism of the time-space evolution of the near-well region secondary hydrate and provide a feasible scheme and technical guidance for the control of the secondary hydrate. The embodiment of the invention is realized in such a way that the experimental device for simulating the secondary formation of the hydrate comprises a reaction unit, a gas injection unit, a liquid injection unit, a temperature control unit, a vacuum degree control unit, an outlet control unit, a gas circulation unit and a data monitoring and processing unit; The reaction unit comprises a reaction kettle, a vacuum box and a constant-temperature water bath box, wherein the reaction kettle is arranged in the vacuum box, and the vacuum box and the reaction kettle in the vacuum box are arranged in the constant-temperature water bath box; The reaction kettle comprises more than two sections of single-section reaction kettles which are cascaded, wherein the inner diameter shrinkage of the more than two sections of single-section reaction kettles is determined based on a similar principle so as to simulate the convergence flow effect that the seepage radius of a hydrate decomposition product is gradually reduced in the near-well region radial seepage process; the gas injection unit is used for injecting gas into the reaction kettle to simulate the gas generated by decomposing the hydrate; the liquid injection unit is used for injecting liquid into the reaction kettle to simulate the liquid generated by decomposing the hydrate; The temperature control unit is used for controlling the temperature in the constant-temperature water bath box; The vacuum degree control unit is used for controlling the vacuum degree in the vacuum box; The outlet control unit is used for controlling the outlet pressure of the reaction kettle and separating and metering gas and liquid generated by experiments; the gas circulation unit is used for conveying the gas separated by the outlet control unit to the gas injection unit again so as to realize the recycling of the gas; the data monitoring and processing unit is used for monitoring and collecting physical parameters in the reaction kettle in the experimental process, wherein the physical parameters at least comprise temperature, pressure and resistivity. Further, any two adjacent sections of the single-section reaction kettles are connected through a reducing flange; The outer end face of the single-section reaction kettle at