Non-subsidence method for developing an in situ oil shale retort

Abstract

A non-subsidence method for developing an in situ oil shale retort tract in a subterranean formation containing oil shale includes forming a number of spaced apart rows of in situ oil shale retorts, leaving intervening zones of unfragmented formation between adjacent rows of retorts for supporting the overburden loads without substantial subsidence. Each retort contains a fragmented permeable mass of formation particles containing oil shale. The retorts in each row are separated by gas barriers that provide support for the overburden load above each row of retorts. After retorting, a stabilizing material is introduced into the void spaces in the spent in situ oil shale retorts for increasing the compressive strength of the fragmented masses of spent oil shale particles in the spent in situ retorts. Thereafter, separate rows of in situ oil shale retorts are formed in corresponding intervening zones of unfragmented formation. The retorts in each intervening row are separated by gas barriers that provide partial support for the overburden load above each row of intervening retorts. Separate barriers of unfragmented formation are left between the retorts in each intervening row and adjacent rows of spent retorts. This shifts the overburden load to the spent retorts and to the intervening barriers of unfragmented formation, as well as to the barriers of formation between individual retorts in the intervening rows of retorts, which collectively support overburden loads without substantial subsidence during the operating life of the retorts in the intervening rows.