To evaluate well connectivity and the impacts on well spacing and long-term production in Bakken, ConocoPhillips has conducted many interference tests which involved alternatively flowing or shutting in adjacent wells in the test pads. This paper will focus on the quantitative interpretation of the interference test data and the insight gained into fracture geometry, well communication and oil recovery. We will highlight how different spacing and development well types, as well as producing time, affect the magnitude of interference observed between wells in the Bakken, and how different data types obtained from interference tests can be integrated.
Several Drilling Spacing Units (DSUs) were identified for the interference tests. The test candidates were selected to cover various situations, including different well spacings, early-time and intermediate-time well lives, and different types of development (new, infill and refrac wells). Valuable data, including downhole Bottom Hole Pressure (BHP) and Timelapse Geochemistry (TLG) samples, were collected during the tests. The first step of the process was to qualitatively analyze pressure interference data to identify trends. Next, an analytical technique involving calculating Chow Pressure Group (CPG) values was applied to develop a workflow of quantifying interference responses between wells. TLG data were interpreted and integrated to verify the observed interference. Finally, a representative reservoir mechanistic model was built and history-matched with the pressure/production data obtained from one of the test wells. This model was used to simulate interference tests at different times of well producing life to validate the CPG approach and gain an insight into fracture geometry and predicted recovery.
Multiple significant insights were gained from analyzing the Bakken interference test data. The key findings include: 1) Tighter well spacing causes stronger cross-well interference due to a larger number of overlapping fractures, leading to higher recovery factors. 2) Well-to-well communication becomes weaker with reservoir depletion, indicating fracture closure and lower long-term drainage efficiency in the far field. 3) The CPG approach is an effective tool to quantify well interference. 4) A reservoir model is used to verify the CPG approach and is useful for integrating interference data and forecasting long-term well performance.
This paper describes the study of cross-well interference between wells in Bakken and comparing the level of interference as a function of well spacing and different times of the producing lives of the wells. The study also involved a novel workflow of integrating pressure and geochemistry data, as well as the use of reservoir simulations to assess the impact of fracture geometry on interference. The combination of analytical and numerical methods of analyzing interference test data can be incorporated into current workflows used for economic evaluation of spacing and completion designs.
This multidisciplinary project involved collaboration between reservoir engineers and geoscientists from multiple asset teams during the collection, analysis, and integration of interference test data.