Cement Design to Optimize Production in a Highly Active Waterdrive Reservoir

摘要

This paper describes the improvement in well production from using advanced well-construction techniques compared to conventional techniques. The advanced technique uses an engineering approach including finite element analysis (FEA), specialized erodability testing, rock mechanics lab testing, and conformance reservoir simulation predictions. In a highly permeable and very mobile water-drive environment where natural hydraulic seal is practically nonexistent, an effective cement sheath imposes a very good mechanical seal to shut the water influx. In this case, the cement sheath is not only a well-construction or pipe-stability issue, it is a final or well-termination product for enhancing well life or last-recovery production. The FEA analysis studies the mechanical interaction among the formation, cement sheath, and casing while applying different stresses on the system. Pressure and temperature changes inside the casing during the life of the well affect the behavior from the cement sheath. To address the performance from the cement system design, the well history for water production requires review. Production and simulated data from reservoir simulators are compared to determine if water production is as expected or not. Conformance reservoir simulators give a good comprehensive criterion to predict water behavior in the reservoir and predict at earlier stages when water will affect well productivity. In the study presented in this paper, three advanced solutions were applied to address an optimization in a highly active water-drive reservoir as: (1) spacer efficiency study, (2) cement-sheath characterization through measured mechanical properties/FEA analysis, and (3) use of conformance simulators to determine the productive capacity of the well. Results are compared with the real production data to determine whether this engineering design improved well productivity. Results of using all new practices were evaluated by CBL logs and production; production results were close to the expected, with low water cut. Yuralpa Field can become uneconomical if cement sheath quality and reservoir standoff to oil-water contact are not suitable.