Determining well-to-well connectivity using a modified capacitance model, seismic, and geology for a Bakken Waterflood

Abstract

Drilling and fracture stimulating horizontal wells in low permeability fields, such as tight oil reservoirs, is a common practice. Estimating the connectivity between these wells (interwell connectivity or IWC) is important for the design and management of a field, especially when waterflood recovery is applied. For example, IWC affects the determination of fracture conductivity and length and can help identify favorable locations for infill drilling and optimize injection rates. In this paper, we show how an alternative method, developed for and successfully applied in conventional reservoirs to determine IWC, can be modified to estimate tight formation IWC using solely production- and injection-rate fluctuations. The model is based on the Capacitance Model, or CM, and is modified to include a pseudo well (CM-PW). The CM-PW is tested with various heterogeneous simulation cases and field data. The CM-PW can identify inter-well heterogeneities. The model accuracy is based on the match to production data and, for all simulation cases, the model accuracy is good with R2≥0.83. The field application, from a tight oil waterflood in the Bakken Formation, shows that the CM-PW results are consistent with tracer test results and field reports showing fracture hits between wells. The CM-PW evaluations also correlate well with the seismically-derived acoustic impedance. Integrating the connectivity analysis with tracer tests, seismic, and the geology enabled us to identify reasons for the connectivity observed, assessing whether injected fluid flows through the reservoir matrix or fractures between injector-producer pairs. To our knowledge, this is the first time the CM has been applied to horizontal wells.