Estimation of fracture production and water breakthrough locations of multi-stage fractured horizontal wells combining pressure-transient analysis and electrical resistance tomography

Abstract

The production of multi-stage fractured horizontal wells (MFHWs) decline fast, and water cut quickly increase after short producing period. How to evaluate well performance and estimate the water breakthrough segments become significant for improving oil recovery. The production logging test (PLT) enables to obtain the production profile along horizontal wellbore, however, it's difficult and expensive to carry out PLT for the MFHW. This work presents a new method to estimate production of hydraulic fractures and determine the water-breakthrough locations by combining pressure-transient analysis (PTA) and electrical-resistance tomography (ERT).This paper presents a PTA model of an MFHW which considers the nonuniform properties of fractures, including unequal fracture conductivity, nonuniform production distribution, asymmetric fractures, and arbitrary locations. The proposed model has been verified with the numerical PTA model in KAPPA Ecrin Saphir software. The type curves are developed and the impact of well and fracture properties on pressure and pressure derivative are also analyzed in detail. When the distance between fractures with high production (FHP) increases or number of FHP decreases, the early-radial flow can be obviously observed, and the duration of this regime depends on the interference among fractures. We define a parameter (N*) to describe the number of FHP, and the N* is determined by properties of hydraulic fractures. N* equals to N (total number of hydraulic fractures) if factures are symmetrically and uniformly distributed along wellbore and have equal production and conductivity. N* approximately equals to the number of producing fractures when all producing factures uniformly distribute along wellbore and have equal production, conductivity, and length. The developed PTA model is used to interpret production of different fractures by matching BHP data. The use of ERT enables to track water front, further estimate the water-breakthrough segments and reduce the non-uniqueness of PTA interpretation. The proposed approach is used to evaluate the well performance of MFHWs from Changqing Oil field, and interpretation results obtained in this work match with the results obtained by PLT.