The severe decline of oil production has been observed in many multi-fractured horizontal wells (MFHW) within only one or two years. It is thus essential to determine production rate distribution of MFHW for improving oil production. However, available pressure-transient analysis (PTA) models of MFHW hardly consider the effect of non-uniform production rate distribution of both horizontal sections and hydraulic fractures on pressure-transient response, which may lead to erroneous results.
This paper aims at presenting an innovative approach to estimate non-uniform production rate distribution along horizontal wellbore in a relatively economical way. A novel model was proposed to better characterize flow in hydraulic fractures and horizontal wellbore. In order to better characterize pressure drops in hydraulic fractures, we first modeled fluid flow in fractures with finite conductivity by two parts, variable-mass-linear flow for fluid far from wellbore and radial flow for fluid near wellbore. Meanwhile, horizontal wellbore with finite conductivity was divided into multiple horizontal sections, and each section is considered as a cylindrical source. As a result, a semi-analytical solution was developed. We further compared it with numerical model to verify the accuracy. A new flow regime (the second radial flow) is discovered and behaves as a flat on pressure derivative curves. It would lead to erroneous results if the new regime is regarded as pseudo-radial flow.
Case study indicated that the production rate distribution obtained by the model proposed in this paper match well with production logging test (PLT), which validated the accuracy of the proposed approach and explored the feasible application in well performance evaluation of MFHW. In addition, operators could make reasonable decisions to improve well performance based on the evaluation results.
