No abstract

Pubei Block, which is a subdivision of Daqing Oilfield, presents a challenging environment for conformance control due to its high temperature (average 80 °C) and salinity (13,451 mg/L), making it difficult for the polyacrylamide-based gel to maintain the necessary gel strength. To address this issue, this study aims to evaluate the feasibility of using a terpolymer in situ gel system that provides greater temperature and salinity resistance and pore adaptation. The terpolymer used here consists of acrylamide, acrylamido-2-methylpropane sulfonic acid, and N,N'dimethylacrylamide. We determined that a formula with a hydrolysis degree of 15.15%, a polymer concentration of 600 mg/L, and a polymer−cross-linker ratio of 2.8 yields the greatest gel strength. The hydrodynamic radius of the gel was found to be 0.39 μm, indicating no conflict with the pore and pore-throat sizes determined by the CT scan. In the core-scale evaluation, the gel treatment improved oil recovery by 19.88%, of which 9.23% was through gelant injection and 10.65% through post water injection. A pilot test began in 2019 and has continued for 36 months until now. Within this period, the oil recovery factor increased by 9.82%. The number is likely to keep going up until the water cut (so far 87.4%) reaches the economic limit.

No abstract

The complex fault block oilfields in the craton basin contain vast reserves of oil and gas resources. During the development of an oilfield, the flow of oil, gas, and water, is controlled by faults and configuration boundaries. The distribution of remaining oil and gas depends on the interpretation of the reservoir’s architecture. However, recognizing the faults and the architecture boundary remains a challenge, hindering the efficient development of these resources. This study proposes a new idea for interpreting the configuration of thick sand bodies. This study was conducted in order to interpret the fine architecture of thick sand bodies in the Sangtamu area, using core samples, well logging, and production data, guided by sedimentation patterns from ancient to modern times. Results indicate that the Sangtamu area is a braided river delta front sedimentary system, dominated by the backbone underwater distributary channel and branch-type underwater distributary channels. The backbone channel is larger in scale, with a relatively large rock grain size and a box-shaped logging curve, whereas the smaller-scale branch channels have a bell-shaped logging curve resulting from the gradual weakening of water energy. Sandstone bodies from different types of underwater distributary channels are spatially overlapped, forming thick plate-like sandstones. The architecture interface between channels can be used as the fluid seepage boundary and can help prevent bottom water intrusion to a certain extent. The remaining oil is primarily concentrated in the architecture boundary area, which presents the next potential tapping area.