Flow diagnosis in variable bottom hole pressure multi-well horizontal pad with well interference using rate/pressure transient analysis

Abstract

Horizontal multi-well pads are frequently used in unconventional reservoirs. Along with infill wells and hydraulic fracturing, interference between multiple multi-fractured horizontal wells (MFHWs) has become a major concern. The current rate transient analysis (RTA) makes the assumption that the unconventional formation contains a single MFHW. This study introduces a novel multi-MFHW solution and associated analysis methodology for analyzing the performance of targeted well rates in a multi-MFHW system.

The constant bottom-hole pressure (BHP) condition and the Laplace transform can be used to obtain multi-MFHW solutions for transient flow. We investigated interference between various fractures and MFHWs using the superposition of various constant BHP solutions. The variable BHP of the targeted well is calculated using a variable dimensionless BHP function in the Laplace domain without performing any convolution or deconvolution. The proposed method is rigorously validated using a commercial numerical simulator for cases involving offset MFHWs and multi-MFHW with variable BHP. With this multi-MFHW analysis, we can analyze a target well in the pad using the total material balance of the multi-MFHW system. Offset well interference frequently occurs following the onset of infinite-acting radial flow (IARF) in the target well's hydraulic fracture. It results in an increase in the pressure derivative curves for elliptical flow and IARF, as well as the rate-normalized pressure (RNP) derivative. Inverse semi-log derivatives exhibit the inverse trend. The proposed deviation pressure integral and RNP can be used to diagnose the flow region caused by the offset well's flow rate in a unique manner, displaying the horizontal line, V-shaped dip, and unit slope, respectively, during IARF, cross flow, and boundary-dominated flow (BDF). Sensitivity analysis of well spacing demonstrates that as well spacing increases, the “transition flow” between wells transitions from elliptical to formation linear flow and can exhibit transitional flow characteristics in more common cases.