Fault characteristics of water-bearing tight condensate gas reservoirs and their effects on development effectiveness: a case study on the Xu 2 gas reservoir in Anyue Gasfield

The reservoir physical properties of tight condensate gas reservoirs are poorer and their gas permeability is lower due to oil, gas and water flow. The recovery factor of tight condensate gas reservoirs is generally lower than 30%. A Fault is the important condition for the high yield of oil and gas, and also the important pathways for water invasion, so it is crucial to figure out the correlation between the characteristics of faults and the development effectiveness of tight condensate gas reservoirs. The gas reservoir of Xu 2 Member in Anyue Gas Field is a water-bearing condensate gas reservoir of low porosity and low permeability. Its reservoir space is mainly acted by residual primary pores and intergranular and intragranular dissolved pores, and fractures are relatively development locally. Their porosity-permeability relationship presents the feature of dual media. Single-well controlled reserve is less. In this paper, the fault characteristics of tight condensate gas reservoirs were analyzed by using the combined method of reservoir engineering theory, core physical simulation experiment and numerical simulation technology. Then, the distribution patterns of faults were classified and their relationships with single-well controlled reserve, decline rate, cumulative production and fluid production characteristics were studied. It is indicated that as for the same fault, its force is different, so its spatial occurrence is different, and the well productivity at different positions of the fault varies greatly. Fractures are more developed at the end of a fault, so the oil production rate of the well located at the end of a fault is 3 times that of the wells drilling the other parts of the fault. In addition, it is fault pattern I in the Upper Submember of Xu 2, fault pattern 2 in the Upper Submember + Lower Submember of Xu 2 Member and fault pattern 3 in the Upper Submember + Lower Submember of Xu 2 Member + Leikoupo Formation. The priority of fault pattern during well arrangement shall be fault pattern 3, 1 and 2, and the end of a fault is the preferred location for well arrangement.