Application of a Gas and Water Drive Combined Characteristic Curvein Reservoirs with Gas Cap and Edge Water

When reservoirs with gas cap and edge water enter the middle and late stages of development, challenges of gas channeling and water cut emerge, and relevant evaluations and development strategy adjustments are needed depending on evaluation results. However, the development effect of such reservoir cannot be directly evaluated by the characteristic curve of gas drive or water drive. In light of this, this paper presents a method for calculating the proportion of oil production by gas drive at different stages by combining the relations for characteristic curves of water drive and gas dive. Specifically, the relation for characteristic curve of gas dive was derived based on the steady seepage theory. The degrees of reserve recovery by gas drive and water drive in reservoirs with gas cap and edge water can be calculated using this method, and the calculation results can provide a basis for adjusting the development strategy. The calculated degree of reserve recovery by gas drive was 24.3% for the upper part of an oil group with gas cap and edge water in Well Block 3 of JZ-X Oilfield, and that by water drive was 48.4% for the lower part. Considering that the degree of reserve recovery by gas drive in the upper part was low, barrier water injection was intended to be conducted for enhancing the oil recovery of the oil group. The research indicates that the development effect of reservoirs with gas cap and edge water can be evaluated by the gas and water drive combined characteristic curve.