Horizontal versus vertical wells interference in hydraulically fractured shale reservoirs

The impact of well interference on in-situ stresses, drainage area, and pressure response in hydraulically fractured shale reservoirs is examined. In-situ stress distribution in the reservoir resulting from fracture propagation and poro-elasticity and its influence on hydraulic fracture orientation and well spacing configurations are studied using iterative numerical methods. The results of the simulation indicated that drainage distance (XDL) from the well centre is restricted to the immediate environment of the well and with little effect on the external reservoir. In contrast, in-situ stress change has a wider and more complex reservoir reach away from the well with stress orthogonal reorientation occurring from a distance-of-stress-orthogonality (Ⱶσ), while pressure response has the farthest reach (XPT). A new approach utilised in this study, which considers in-situ stress, drainage area and pressure interference (such that XDL< Ⱶσ < XPT), suggests that a spacing range of 450ft to 750ft, with an optimum of 600ft for minimal interference will be adequate. Furthermore, parallel orientation of infill wells within this range is less feasible due to complex stress reorientation over the productive years. Wells drilled and fractured perpendicular to the parent well showed incremental cumulative production.