Qualitative Discuss on Well Test Curve Uncertainty Analysis in Remaining oil Evaluation of Thick Bottom Reservoir

In directional wells of thick bottom water reservoir, partial perforation is usually applied to prevent rapid coning of bottom water. Because of the existence of interlayers, water driving conditions and remaining oil distribution become complex. In partially perforated wells in the survey area oil saturation of lower unperforated section can’t be tested directly due to the influence of completion structure. The "spherical flow" characteristics cannot be seen from the pressure derivative curve during the pressure building. The uncertainty analysis of well-test curve is used in the analysis of interpretation model, Kz/Kr value and boundary feature. The results show that the unperforated section at the lower part, slightly affected by the water flooding, contributes less to oil production. Through the study on reservoir numerical simulation mechanism, it’s concluded that in oil wells driven by bottom, water cut features rapid rise in early stage and slow rise in later stage. The water cut rise curve mainly belongs to a convex type. In contrast, in oil well driven by edge water, water cut rises slowly in early stage but rapidly later. The water cut curve is mainly a concave type. The research well shows a concave type in the water cut curve. Test data shows the well is driven by edge water under the influence of interlayer. The unperforated section at the lower part of reservoir where the remaining oil concentrates can become the target of further tapping.