Abstract:

The ultra-deep fault-controlled fractured-vuggy gas reservoirs in the Tarim Basin represent a principal option for increasing gas reserves and production. It is crucial to determine the reasonable productivity of gas wells for the efficient development of gas reservoirs. Shunbei ultra-deep fault-controlled fractured-vuggy gas reservoir is characterized by strong heterogeneity, high stress sensitivity, and varying physical properties, therefore, conventional methods for determining reasonable productivity of the reservoir need to be improved. Based on geological and production data, the reservoirs in the F1 zone of the Shunbei gas reservoir can be divided into three types: fault + cavity, fault + pore, and fault/fracture. According to the calculation by the binomial productivity equation for wells in high-pressure gas reservoirs, the fault + cavity reservoir show the highest absolute open flow potential (AOFP), followed by the fault + pore reservoir, and then the fault/fracture reservoir. The productivity test curves show 3 shapes such as linear, upward curved, and downward convex, with the reasonable choke as the largest choke within the testing range for the former two shapes, and as the choke at the inflection for the downward convex shape. The pressure drop method shows that, within the testing range, a larger reasonable choke is preferred for the fault + cavity reservoir, and a smaller reasonable choke for the fault + pore and fault/fracture reservoirs.

Key words: Tarim Basin, ultra-deep stratum, fault-controlled fractured-vuggy gas reservoir, reasonable productivity, productivity test method, pressure drop method