The influence of the water injection method on two-well-horizontal salt cavern construction

With high construction efficiency and large usable volumes, underground TWH caverns in rock salt formations provide optimal storage for large-scale compressed natural gas. Previous studies of SWV cavern construction indicate that different water injection methods will result in different leaching rates and will therefore form different cavern geometries. Therefore the influence of the water injection method on the TWH cavern construction process and geometries were thoroughly evaluated in this study. Based on the leaching numerical simulation code TWHSMC V2.0, we conducted a series of simulation experiments. The results illustrate that under the same water injection rate, the cavern construction speed of the alternate injection method is faster than the unidirectional injection method. Using the unidirectional method will form asymmetrical triangular pyramidal caverns. In contrast, using the alternate method will form symmetrical elliptical cone caverns. Under repeated alternating “Injection” and “Withdrawal” operations, the larger the flow rate, the shorter the cavern construction time, and the smaller the H/L ratio coefficient, as well as the closer the cavern geometry is to the horizontal cavern. Thus, during construction of a TWH-cavern in thinly-bedded rock salt (halite) deposits, repeated and alternating injections and withdrawals with high flow rates are necessary.