Development specifics of fields complicated by tectonic faults

The paper explores impact of fault conductivity on development dynamics of oil reservoir under depletion drive. It also presents comparison of sealing faults and capillary barriers. In both cases, the fault is identified both by the presence of amplitude shifts and by the difference in water-oil contact levels in the adjacent sections of the deposit. The study is conducted on a 3D flow simulation model of a hypothetical hydrocarbon deposit based on the initial data for one of the fields in West Siberia. The results of the simulation show that erroneous estimates of the fault conductivity may lead to an incorrect choice of the field development system and the sequence of wells drilled, which significantly affects production performance and recovery of reserves.
Materials and methods
The study was performed on the basis of literature analysis and numerical simulation using the 3D model of a hypothetical oil deposit with parameters attributed to one of the fields in West Siberia.
Results
If displacement of rocks along the fault surface led to a sharp change in the capillary properties of the formation across the fault, then differences in the fluid contact levels may indicate both non-conductivity of the fault and presence of capillary barrier, although its conductivity may remain. The obtained findings of simulation under natural recovery drive show that both cases reveal significant differences in basic development parameters, fluid distribution pattern and pressure with respect to oil recovery in both developed and undeveloped area.
Сonclusions
Despite the large amount of accumulated research findings on faults, understanding of their potential influence on the field development process is practically reduced to the issue of fault conductivity. The main criterion is a noticeable difference in the fluid contact levels in the fault-adjacent sections of the deposit and typical formation boundary, revealed in pressure curves during pressure transient tests. However, both criteria cannot reliably verify conductivity or non-conductivity of the fault. At the same time, faults may have significant impact on the processes in the reservoir during hydrocarbon production, and the degree of such impact heavily depends on the conductivity of the tectonic zone. The obtained results indicate necessity for more thorough and comprehensive study of the data at the stage of modeling and reservoir engineering in the context of deposits with faults. Erroneous assessment of the fault conductivity may lead to serious errors in the field development strategy, which in turn affects the economics of the project and ultimate oil recovery.