Stability analysis of a typical two-well-horizontal saddle-shaped salt cavern

To increase natural gas storage capacity and further utilize salt mine resources, salt cavern gas storage in the Yunying salt mine, Hubei Province, China, was simultaneously constructed in two different mining layers (K3 and K4). The purpose of this study was to investigate the long-term feasibility of operating salt caverns for gas storage in two mining layers. Based on the geological conditions and sonar test results, the geometric parameters for the salt caverns in the two mining layers were designed, and a 3D geomechanical model was built to predict the cavern stability. The corresponding evaluation index included the displacement, volume shrinkage rate, equivalent strain, and dilatancy factor. The results show that simultaneously operating salt cavern gas storage in two mining layers is feasible, and the operational pressures for the salt caverns in mining layers K3 and K4 should be no less than 4–9 and 7–12 MPa, respectively, to satisfy the stability requirements. The surrounding rock of the salt caverns presents a larger displacement and volume reduction compared with cases in which the salt caverns are operated in a single mining layer. Increasing the injection–withdrawal frequency increases the deformation of the surrounding rock.

Section: Equivalent Strainmentioning

confidence: 99%

Section: Dilatancy Factormentioning

confidence: 99%

Stability Evaluation of Horizontal Salt Caverns for Gas Storage in Two Mining Layers: A Case Study in China

Zhao,

Ma,

et al. 2023

“…It is applicable to both plastic rock and brittle rock shear failure and also points out the characteristic that the tensile strength of rock is far less than its compressive strength. This theory is widely used in rock engineering practice [10,19].…”

Section: Elastic-plastic Constitutive Modelmentioning

confidence: 99%

Stability Analysis of a Typical Salt Cavern Gas Storage in the Jintan Area of China

Wan

Liu

et al. 2022

Using underground space to store natural gas resources is an important means by which to solve emergency peak shaving of natural gas. Rock salt gas storage is widely recognized due to its high-efficiency peak shaving and environmental protection. Damage and stress concentrations inside the cavern injection during withdrawal operations and throughout the storage facility life have always been among the most important safety issues. Therefore, accurate evaluation of the stability of rock salt gas storage during operation is of paramount significance to field management and safety control. In this study, we used the finite element numerical analysis software Flac3D to numerically simulate large displacement deformations of the cavern wall during gas storage—in addition to the distribution of the plastic zone of the rock around the cavern and the surface settlement—under different working conditions. We found that the maximum surface settlement value occurred near the upper part of the cavern. The surface settlement value increased as a function of creep time, but this increase leveled off, that is, a convergence trend was observed. The value was relatively small and, therefore, had little impact on the surface. The application of gas pressure inhibited the growth of the plastic zone, but on the whole, the plastic zone’s range increased proportionally to creep time. For the 20-year creep condition, the deformation value of the cavern’s surrounding rock was large. Combined with the distribution of the plastic zone, we believe that the cavern’s surrounding rock is unstable; thus, corresponding reinforcement measures must be taken.

“…However, the lateral span of the horizontal-well cavity is greater and there are more factors involved in the long-term stability of the salt-cavity natural gas storages [15,16]. Zhang et al [17][18][19][20] investigated the stability of the surrounding rock of a horizontal-well natural gas storage. Li et al [21,22] investigated the comparison of the safety and stability of cavities with different morphologies used to store different energy sources.…”

Section: Introductionmentioning

confidence: 99%

Comprehensive Research on Construction and Stability of Horizontal-Well Cavity Natural Gas Storage in Thinly Bedded Salt Rocks in China

Lu,

Chen,

et al. 2023

Self Cite

This study aimed to overcome the difficulty of conducting the horizontal-well cavity leaching test in the field and to investigate the long-term stability of the horizontal-well salt-cavity natural gas storage. The simulation test design is combined with the similarity theory to study the cavity expansion characteristics and the influence law of cavity leaching parameters. Through the design of a rubber hose connection, an integrated closed test system for multi-stage horizontal-well cavity leaching and brine drainage was built. The test system also realises the repeatable backward movement of the injection well during the test. A similarity simulation of the test design was carried out, and the test platform was constructed to carry out multi-stage horizontal-well leaching tests with a nitrogen cushion. In the horizontal-well leaching tests with a nitrogen cushion, the influence laws of the well spacing, flow rate and liquid level position on cavity expansion were investigated. Based on the morphological characteristics of the horizontal-well cavity, a numerical model of the horizontal-well salt cavity was developed, which reflects the real cavity morphology leached in the test. The long-term stability of the horizontal-well salt-cavity natural gas storage under different internal pressures was investigated through numerical simulation.