Tertiary recovery of oil by up-dip gas injection.

摘要

A tertiary gas injection process denotes the mobilization of waterflood residual oil by gas invasion; whereas, secondary gas injection denotes the displacement of a continuous oil phase by gas. The term up-dip gas injection implies that the gas is injected in the crest of the structure in order to displace fluid down-dip where it can be recovered in a production well; whereas, an attic oil recovery process usually implies a cyclic injection/recovery process using a single well. The objective of this study is to develop a technique for modelling relative permeability in a tertiary gas injection process occurring in a high permeability, strongly water-wet sandstone reservoir for which gravity effects may be significant.; The relative permeability modelling technique was developed based on the following: (1) published two-phase relative permeability data measured by conventional techniques, (2) published oil relative permeability data derived from in-situ saturation measurements, and (3) agreement between the predictions of a linear numerical simulator and the production observed during a previous laboratory study at LSU. The numerical modelling study indicated that the production behavior observed during the laboratory study can be accurately predicted using a simple power-law relationship between relative permeability and saturation.; By incorporating the new relative permeability modelling procedure into a simple streamtube model, a simplified approach for screening tertiary gas injection candidates was developed. To illustrate its application, this simplified approach was applied to one of the fault blocks involved in the West Hackberry Tertiary Project. Based on the predictions of the screening model, the degree of stratification exhibited by a reservoir plays a major role in the efficiency of a tertiary gas injection process.