Influence of Sand Production in an Unconsolidated Sandstone Reservoir in a Deepwater Gas Field

Abstract

In an unconsolidated sandstone reservoir of a deepwater gas field, due to the reduction of the rock compaction by deepwater, sand production is more likely to occur in the reservoir during production under certain production pressure differences. Therefore, it is important to accurately control the production pressure difference. A theoretical analysis model of sand production was established. On the basis of the model, the critical production pressure difference and the critical flow rate of the sand production were tested through indoor simulated experiments of sand production of three-dimensional full-diameter core. In addition, the critical production pressure difference for the sand production with an open hole completion was verified by means of numerical analysis. The analysis procedures and results are as follows: (1) based on the production test, the gas flow rate and the sand production rate under various production pressure differences were measured. It was found that the critical production pressure difference of core of target block was about 2 MPa, which is lower than the critical sand production pressure difference of core in shallow water or land. (2) A finite element analysis model was established by means of a theoretical analysis on the basis of core mechanics testing, and the analytical model was validated by comparing the experimental model and the theoretical model. A plastic deformation criterion for sand production was proposed. (3) The sand production model of the deepwater reservoir was established based on field parameters. The primary parameters that affect the rock strength were analyzed using the sand production criterion, which was verified by the experimental and numerical simulation results. Analysis results show that the effect of cohesive compared with elastic modulus, Poisson's ratio, and angle of internal friction on sand production is greater. At the same time, it should also pay attention to the influence of the drilling and production process on sand production.