As has been demonstrated recently, flowback data from multi-fractured horizontal wells (MFHWs) can be analyzed to provide early estimates of reservoir and hydraulic fracture properties. However, MFHWs in close proximity (e.g., drilled from the same well pad) can experience inter-well communication through hydraulic fractures. The communication between wells can significantly impact well production forecasting, reserves estimation, and design optimization. In this study, dynamic (contacted) fluid-in-place (CFIP) calculations are performed using flowback and early-time production data to quantify the productivity loss of a parent well when a child well comes on production.
Rate-transient analysis theory can be used to derive the CFIP of a well producing at variable pressures/rates. However, previous studies that have used this approach have assumed single-phase flow. Because multi-phase flow can occur during flowback/early-time production, this must be corrected for in the CFIP calculations. Two approaches were pursued herein for this purpose: the total volumetric flow rate (combined phase) approach and the modified pseudovariable approach. To compare these approaches, multiple numerically-simulated examples were used. Two-phase flowback production scenarios were simulated, where the parent and child wells were assumed to be communicating through a hydraulic fracture with a specified transmissibility multiplier (Tmult) used to adjust the amount of inter-well communication. For high connectivity (Tmult > 0.25) scenarios, application of the combined phase approach resulted in estimates of the parent well CFIP reduction (caused by child well production) of ∼46-50%, whereas application of the modified pseudovariable approach resulted in estimates of ∼49-51%. For the low connectivity case (Tmult = 0.001), these estimates were ∼11% and ∼8%, respectively, for the two approaches. Therefore, for the simulation cases studied herein, the two approaches agreed within acceptable error. Numerical simulation was also used to verify the absolute change in CFIP using these two approaches for correcting for multi-phase flow.
Practical application of the modified CFIP method was demonstrated using two field cases with flowback/early-time production. Both field cases demonstrated that changes in CFIP for the parent well can be unambiguously interpreted. For flowback data obtained for two communicating wells completed in a western Canadian tight oil reservoir, the reduction in CFIP of the parent well (caused by the child well) was estimated to be ∼83% using the combined phase approach, and 82% using the modified pseudovariable approach; therefore, for this case, the two approaches yielded similar results. For early-time production data associated with Well 23 of the SPE data repository, the reduction in CFIP of the parent well (assumed to be caused by an offset well) was estimated to be ∼37% using the combined phase approach, and 40% using the modified pseudovariable approach.
This study demonstrates for the first time that dynamic fluid-in-place calculations for the parent well during flowback and early production data can be analyzed to quantify inter-well communication. A simple yet rigorous method is provided for estimating changes in the parent well CFIP caused by a child well early in the production life.