Waterflood Direction and Front Characterization With Four-Step Work Flow: A Case Study in Changqing Oil Field China

Because of the effect of reservoir heterogeneity and fractures in low-permeability reservoirs, effective characterization of waterflood direction and front has become a challenging issue under high-water-cut condition. To achieve better understanding of such a complex problem, a work flow, containing statistical and numerical techniques, is developed to characterize waterflood direction and front distribution in Changqing oilfield by using both flow rates and bottomhole-pressure (BHP) data. The work flow includes four steps: First, dynamic analysis is used to qualitatively investigate the relationships between injector and producers; then, the constraint multiple-linear-regressions (MLR) method is applied to calculate the interwell-connectivity coefficients, which was used to quantitatively describe the waterflood direction by production and injection rates. On the basis of the results of the two former steps, we can adopt numerical well testing as our third step to deal with flow rates and BHP data to characterize the waterflood direction and front. Finally, the streamline method is used to simulate the waterflood front and high-permeability-channel distribution on the basis of the outcome of the three preceding techniques. Compared with individual methods, the proposed work flow can offer more perspectives and ways to make a comprehensive and deep investigation of the waterflood reservoir. The results obtained by this work flow enable proactive and better waterflood management in the Well Group W16 in Changqing oil field; namely, the water cut of producers decreases, meanwhile the oil production increases by nearly 40% referring to the field data in 2015. With the help of the information obtained by this work flow, operators could make more-reasonable decisions on waterflood management such as well-pattern optimization and injection-production parameters adjustment.