Abstract

Salt beds in China have typical features such as low grades and multi-interlayers. During leaching, a large amount of insoluble sediments fall down to the bottom accounting for 1/3 up to 2/3 of the storage capacity. It is of urgency to investigate swelling laws of these insoluble sediments and search for suitable chemicals to effectively control storage capacity loss. In this paper, XRD was used to analyze mineral composition at first. Then, referred to the novel evaluation method for deposit shrinkage, clay swelling and physical deposit shrinking experiments were conducted to measure the contributions of various swelled-clay-shrinking agents, agent concentrations and deposit meshes to free water content. The results showed that SA2# was the most suitable agent and the peak shrinkage was up to 30.02%, which is equivalent that the gas storage with 1.5 million m3 can enlarge effective cavity volume by at least 150,000 m3. This paper proposes a chemical method to drain free water from the voids of insoluble sediments at the bottom of salt cavern guiding a new direction to enlarge effective space for salt cavern gas storage.

Introduction

Natural gas is playing an increasingly important role in China's energy consumption as a clean energy source (M.Y. Gao et al., 2015). Salt cavern underground gas storage is formed by water dissolution in the salt layer or salt mound to store natural gas (L.N. Ran et al., 2017). The underground salt cavern gas reservoir has the advantages of large single-cavity storage capacity, fire and explosion-proof, pollution prevention and rapid injection and recovery conversion, which is very suitable for China's strategic natural gas reserves and important emergency peak mobilization facilities (G. Jing et al., 2017).

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