Local Stress Shadow Effect Analysis in Multistage Hydraulic Fracturing Design Considering Small Drillhole Spacing

Abstract

In this paper, the effect of local changes in the stress-strain state of rocks is analyzed, and an appropriate approach is proposed for modeling the geometry of hydraulic fractures on horizontal wells under conditions of a dense drilling network, including Zipper Frac technology. The main source of factual information on the development of cracks are the pressure curves obtained during injection tests, mini-fracs and main frac jobs, including fracs on offset wells and microseismic monitoring of fracturing. At Vinogradov field as the optimal selected row production system. The analysis of the accumulated experience made it possible to identify promising areas for increasing the efficiency of the production system, including reduction in the distance between rows, a change in well azimuths relative to the principal stresses, and the extension of horizontal sections of the wells. In this paper, we analyze the results of multi stage HF in conjunction with modeling the geometry of cracks in various software products, taking into account and without taking into account the local change in the stress-strain state of the rocks near hydraulic fractures. The simulation results are cross-validated with actual information on the various wells of the development object under consideration. Modeling and analysis of the geometry of cracks in neighboring wells, oriented both longitudinally and transversely with respect to the direction of maximum horizontal stress, is carried out. Including the mutual influence of stages of Zipper Frac technology is analyzed. Taking into account the effect of local stress redistribution made it possible to achieve a high degree of correspondence between the results of modeling available actual information from the target wells and the environment wells (pressure responses, microseismic results and production figures). Without taking this effect into account, it was not possible to achieve such a degree of compliance. The conclusion is made that the effect of local stress redistribution both during fracturing at adjacent ports of a single horizontal well and fracturing of adjacent horizontal wells has significant influence on geometry and, in particular, to the fracture height, which is critical in the geological conditions of the considered object. An approach to modeling and planning of the multi stage frac on horizontal wells in conditions of complex reservoirs similar to the object under consideration was developed. In particular, new approaches to the optimization of the sequence of Zipper Frac stages are proposed and recommendations are made for carrying out fracturing in the conditions of both longitudinal and transverse drilling mesh in relation to the direction of the maximum horizontal stress.