Construction modeling and shape prediction of horizontal salt caverns for gas/oil storage in bedded salt

Abstract

Construction modeling and shape prediction are significant for the parameters optimization and capacity prediction of a horizontal salt cavern gas/oil storage. However, most previous studies concentrate on the middle segment of the cavern, and the insoluble substances are ignored. The actual shapes of the horizontal salt caverns in bedded salt remain unknown. Here a coupled model is proposed for the construction of a horizontal cavern. A composite structural mesh is presented to describe the development of three segments of the cavern. The equations of the salt-brine mass transfer rate and boundary movements are introduced. A simplified flow and concentration field model is presented. The accumulation of the insoluble substances is firstly considered in a horizontal cavern. A VC++ program using the finite volume method is developed to obtain the numerical solution of the model and as a construction design tool for the horizontal salt caverns. The reliability of the model and program has been confirmed by comparisons with laboratory experiments. The shape of a field horizontal cavern HA4-5 in Huai'an, China is successfully simulated. The simulation results coincide well with the field data. It is found that the horizontal cavern is actually U-shaped and there is an undetected open cavern in the middle segment. This cavern is suggested to be used as a non-clogging de-brining pool during gas/oil injection and brine discharge. The brine in the pores of the insoluble sediments will be replaced by gas/oil and the storage capacity will be multiplied. The finding promises a broad prospect for the horizontal salt cavern gas storage in bedded salt.