Induced Flow Geometries During Steam Injection in Unconsolidated Sand in Heavy and Extra-Heavy OiI Fields in Mexico

Abstract

Abstract This objective of this paper is to demonstrate that transient linear flow is the dominant behavior in unconsolidated sands performing under steam injection in Mexico. It has been observed in the past and there is evidence from fall-off tests that all wells injecting water in unconsolidated sands that store heavy oil exhibit a condition similar to being fractured. Apparently, this is the result of high mobility around the fracture. Something similar can occur during the processes of cyclic steam and continuous steam injection in unconsolidated sands. This is investigated in detail in this paper with different types of transient pressure tests. The paper presents the analysis of falloff, injection and interference tests carried out in steam injection wells in an unconsolidated sand that stores extra-heavy oil. Subsequent to a series of steam injection cycles, the well exhibited a transient pressure behavior that is characteristic of linear geometry. The boundary of the linear flow behavior is associated with the extra-heavy oil zone not affected by steam. Furthermore, subsequent to a period of continuous gas injection (as opposed to the previous cyclic gas injection), it was observed that linear flow was prevalent again. In addition, an interference test was carried out between the injection well and another well producing from the same unconsolidated sand. The interference pressure signal at short times showed a behavior that corresponds to linear flow. The test also permitted to estimate the compressibility of the unconsolidated sandstone. Based on the evidence collected during the different tests, the conclusion is reached that during the processes of steam cyclic and steam continuous injection, a channel of high oil mobility was generated by the viscosity contrast of water and extra-heavy oil. This channel is limited by oil zones not affected by steam. The novelty of the paper is demonstrating that transient linear flow is prevalent throughout the fall-off, injection and interferences tests in the Mexican unconsolidated sand. It is likely that the same observation might have application is other unconsolidated sands undergoing steam injection.