CN-121993255-A - System and method for preventing gas channeling of sediment and brine discharge at bottom of salt mine old cavity

CN121993255ACN 121993255 ACN121993255 ACN 121993255ACN-121993255-A

Abstract

The invention provides a gas channeling prevention system and a method for removing sediment and brine at the bottom of a salt mine old cavity. The gas channeling prevention system comprises a gas injection and production shaft used for injecting gas and producing gas in the process of gas injection and brine discharge, a brine discharge shaft production sleeve used for injecting water and discharging brine in the process of gas injection and brine discharge, a water injection pipe used for injecting water into the old cavity after gas channeling, a check valve used for preventing bottom hole gas from channeling upwards along the water injection pipe towards a wellhead, a pressure gauge and a gate valve used for closing or opening a brine discharge channel in the brine discharge process, wherein the gas injection and production shaft production sleeve and the brine discharge shaft production sleeve are connected with the old cavity, the brine discharge shaft production sleeve is sleeved on the outer side of the water injection pipe, a gap is reserved between the brine discharge shaft production sleeve and the water injection pipe, the check valve is installed at the bottom of the water injection pipe, and the pressure gauge and the gate valve are connected with the top of the brine discharge shaft production sleeve through pipelines.

Inventors

FU PAN
SONG HENGYU
Pang Yuhan
REN SHIJU
DIAO HAOYU
CHANG ZHI
XIA YAN
YUAN GUANGJIE
LIU TIANEN
WANG XIANGYANG
BAN FANSHENG
LI GUOTAO
ZHUANG XIAOQIAN
Guan Yueyang

Assignees

中国石油天然气集团有限公司
中国石油集团工程技术研究院有限公司

Dates

Publication Date: 20260508
Application Date: 20241101

Claims (10)

1. The gas channeling prevention system is characterized by comprising a gas injection and production pit shaft for injecting gas and producing gas in the process of gas injection and brine discharge, a brine discharge pit shaft production sleeve for injecting water and discharging brine in the process of gas injection and brine discharge, a water injection pipe for injecting water into the old pit after gas channeling, a check valve for preventing bottom hole gas from channeling upwards along the water injection pipe towards a wellhead, a pressure gauge and a gate valve for closing or opening a brine discharge channel in the brine discharge process, wherein the gas injection and production pit shaft and the brine discharge pit shaft production sleeve are connected with the old pit, the brine discharge pit shaft production sleeve is sleeved on the outer side of the water injection pipe, a gap is reserved between the brine discharge pit shaft production sleeve and the water injection pipe, the check valve is arranged at the bottom of the water injection pipe, and the pressure gauge and the gate valve are connected with the top of the brine discharge pit shaft production sleeve through pipelines.
2. The system for preventing gas channeling by removing sediment and brine from the bottom of an old cavity of salt mine according to claim 1, wherein the injection well bore is connected with the top of the old cavity, and the brine removing well bore production sleeve is connected with the bottom or side of the old cavity.
3. The system for preventing gas channeling of salt mine old cavity bottom sediment and brine discharge is characterized in that a water injection pipeline is connected to the top of a water injection pipe, a water injection pump is connected to the water injection pipeline, a ground gas injection system is connected to a water injection well shaft, a brine discharge well head is arranged at the top of a brine discharge well shaft production sleeve, an old cavity upper cavity is arranged at the top of an old cavity, and old cavity bottom sediment is arranged at the bottom of the old cavity.
4. The gas channeling prevention system for removing sediment and brine from the bottom of a salt mine old cavity according to claim 1, wherein the gate valve is connected with a throttle valve group through a pipeline, and the throttle valve group is connected with a gas-liquid separation device for separating gas-liquid two-phase flow through a pipeline.
5. The system for preventing gas channeling of salt mine old cavity bottom sediment and brine discharge according to claim 4, wherein the bottom of the gas-liquid separation device is connected with a brine return pipe, the brine return pipe is connected with salt mine, and the top of the gas-liquid separation device is connected with a venting system.
6. The system for preventing gas channeling of salt mine old cavity bottom sediment and removing halogen according to claim 4, wherein the throttle valve group comprises a pair of throttle valves and a pair of flowmeters, the throttle valves are connected in parallel and then connected with the gate valve through pipelines, and the flowmeters are arranged on the pipelines between the throttle valves and the gate valve in a one-to-one correspondence.
7. The system for preventing gas channeling of salt mine old cavity bottom sediment and brine discharge according to claim 1, wherein the brine discharge shaft production casing is coaxially arranged with the water injection pipe.
8. The method for preventing gas channeling of the sediment and the brine discharge at the bottom of the salt mine old cavity is characterized by comprising the following steps of: s1, injecting planned storage gas into an injection and production shaft so that the planned storage gas drives brine in an old cavity to move downwards; S2, preventing the planned storage gas from moving upwards through the water injection pipe through a check valve, so that the gas can only move upwards along a gap between the halogen-discharging shaft production casing and the water injection pipe; S3, when the pressure gauge displays pressure, the gas-liquid interface is positioned below the bottom transverse depth of the halogen-discharging shaft production casing, and brine is injected into the old cavity through the water injection pipe until the gas-liquid interface is positioned above the bottom transverse depth of the halogen-discharging shaft production casing.
9. The method for preventing gas channeling by removing halogen from sediment at the bottom of a salt mine old cavity according to claim 8, wherein the method comprises the following steps of: S4, throttling gas and liquid two-phase flow which upwards flow to an annulus between the halogen-removing shaft production casing and the water injection pipe through a throttle valve, and measuring the flow of the flowing gas and liquid through a flowmeter; S5, separating the gas and liquid two-phase flow through a gas-liquid separation device; s6, venting the gas in the gas and liquid two-phase flow through a venting system; and S7, draining the liquid in the gas and liquid two-phase flow to the salt mine through a halogen return pipe.
10. The method for preventing gas channeling of salt mine old cavity bottom sediment and brine discharge is characterized in that in the step S1, planned storage gas is injected into an injection and production shaft through a ground gas injection system, so that the planned storage gas drives brine in the old cavity to move downwards, when a gas-liquid interface is above the bottom transverse depth of a brine discharge shaft production sleeve, gas injection and brine discharge are safely carried out, in the step S3, when a pressure gauge displays pressure, a water injection pump is started, brine is injected into the old cavity through a water injection pipeline and a water injection pipe until the gas-liquid interface is above the bottom transverse depth of the brine discharge shaft production sleeve, and water injection is stopped.

Description

System and method for preventing gas channeling of sediment and brine discharge at bottom of salt mine old cavity Technical Field The invention relates to the technical field of salt cavern underground storage building, in particular to the technical field of salt cavern underground storage building. Background The salt cavern reservoir has complex geological conditions, the salt cavern underground reservoir is mostly built in a layered salt-containing stratum consisting of a soluble salt layer and an insoluble interlayer, insoluble substances contained in the stratum are peeled off, collapsed and expanded to be accumulated at the bottom of a cavity to form residues in the process of water-soluble cavity making, so that part of the space of the cavity is occupied, and the gas storage volume is reduced. According to the residue conditions of 5 salt mine design cavities in certain areas, the height range of the residue is 52.4-120.7 m, the average height is 74.2m, the average height ratio of the built cavities is 47.9%, and the volume ratio of the residue is 46.8%. Meanwhile, combining with the cavity-making experience of a certain saline mine, the accumulation coefficient of the residues is about 1.6, if the expansion coefficient of insoluble particles measured by component analysis of a salinization enterprise is calculated to be 1.2, 25% of the space in the residues is filled with pore water, and if the pore water can be displaced and utilized, the gas storage space of the cavity is enlarged, the utilization efficiency of the saline cavity is improved, and the warehouse-building investment is further reduced. The existing salt cavity residue space brine discharge method mainly enters the modes of residue brine discharge, chemical separation and the like through a secondary brine discharge tool, and the field implementation difficulty is high. Another technical idea is to communicate with the original old cavity at the side or bottom of the old cavity of the salt mine by means of new drilling or dissolving cavity, so as to realize gas injection and brine discharge of the upper cavity and the bottom sediment space of the old cavity and to maximize the utilization of the salt cavity space, as disclosed in patent CN107905844B, a method for gas injection and brine discharge of the full mining space of the old cavity of the salt mine is disclosed. The technical idea is to utilize a newly drilled brine discharging well to discharge brine, and in the actual gas injection process, the technology of the existing gas-liquid interface monitoring means is not mature, so that the gas-liquid interface cannot be monitored and predicted when gas is injected below a sediment surface, and gas is easy to flow up along the brine discharging well shaft, so that the safety risk is extremely high. Disclosure of Invention Aiming at the defects of the prior art, the invention provides a system and a method for preventing gas channeling of sediment and brine discharge at the bottom of an old salt mine cavity. The technical scheme includes that the gas channeling prevention system comprises a gas injection and production shaft for injecting gas and producing gas in the process of gas injection and brine discharge, a brine discharge shaft production sleeve for injecting water and brine discharge in the process of gas injection and brine discharge, a water injection pipe for injecting water into the old cavity after gas channeling, a check valve for preventing bottom hole gas from channeling upwards along the wellhead direction of the water injection pipe, a pressure gauge and a gate valve for closing or opening a brine discharge channel in the brine discharge process, wherein the gas injection and production shaft and the brine discharge shaft production sleeve are connected with the old cavity, the brine discharge shaft production sleeve is sleeved on the outer side of the water injection pipe, a gap is reserved between the brine discharge shaft production sleeve and the water injection pipe, the check valve is arranged at the bottom of the water injection pipe, and the pressure gauge and the gate valve are connected with the top of the brine discharge shaft production sleeve through pipelines. The technical scheme has the beneficial effects that the injection and production shaft is used for the gas injection and production channel in the gas injection and halogen discharge process. The brine discharge shaft production casing is used for injecting water and discharging brine in the gas injection brine discharge process. The water injection pipe is used as a water injection channel after gas channeling. The check valve is used to prevent bottom hole gas from channeling upward along the water injection pipe toward the wellhead, and only allows fluid to flow from the wellhead to the bottom hole along the water injection pipe. The gate valve is used for closing or opening the halogen discharge channel in the halogen discharge process. T