Optimization and Evaluation of Chemical Shrinking Agent for Deposits in Salt Cavern Gas Storage

Abstract

Abstract Salt cavern gas storage is an important strategic method to shave the fluctuation of supply-demand of natural gas in China. However, due to low grades of salt beds, there remains lots of insoluble sediments accounting for 1/3 up to 2/3 of the storage capacity at the bottom of cavity. The use of chemical agent with the function of swelled-clay-shrinking is an effective method for enlarging actual cavity volume. Clay swelling and physical deposits experiments were conducted to select the suitable chemical shrinking agent and study the relation between salt rock and agent. A device simulating the leaching process of insoluble sediments was developed to evaluate different factors on residue deposits and XRD (X-Ray Diffraction) was used to analyze mineral compositions of various salt caverns. The results showed that the main controlling factor for the volume swelling of the bottom insoluble sediments in the salt cavity is the electrostatic repulsion. These hydrated cuttings carry a negative charge leading to the electrostatic repulsion between each other, which promotes the loose accumulations of these physical deposits. The relation between rock and shrinking agent is clarified and the selected chemical agent has an excellent adaptation in salt cavern gas storages through the tests above. In addition, the result provides an experimental basis for minimizing the volume of the salt carven sediments to store more natural gas.