A Novel Method for Predicting Productivity of the Multi-stage Fractured Horizontal Well with Tighter Clusters in the Heterogeneous Tight Oil Reservoir and Its Applications

Abstract

AbstractProductivity prediction is crucial to multi-stage fracturing optimization design of the horizontal well with tighter clusters. In order to quantify the impact of non-uniformly propped fractures created by stimulation and the induced micro-fractures around them on well productivity and sequentially predict it accurately. The permeability field function is firstly introduced to characterize the non-uniform proppant distribution and matrix heterogeneity due to the induced micro-fractures. A novel analytical method, for predicting multi-stage fractured horizontal well is firstly proposed using Laplace transformation and Stehfest inversion with considering the tight reservoir heterogeneity. This proposed model is validated by comparing the calculated production with a field case. The fracture controlling index is defined, denoting oil production in a single fracture per unit fractured horizontal lateral length. The effect of the non-uniform propped fractures, fracture spacing, and fracture length on the fracture controlling index is analyzed. It is shown that higher uneven distribution of proppant placement in the fracture decreases the fracture controlling index. Improving the uniformity of proppant placement in the fracture results in higher productivity when the proppant concentration in the fracture near the wellbore is ensured; Lowering fracture spacing inevitably decreases single fracture’s drainage area, however, fortunately increases the fracture controlling index. With the same treatment scale, shortening the fracture length and simultaneously increasing fracture clusters can improve the proppant placement distribution, resulting in higher fracture controlling index. The method proposed in this paper for predicting production of the multi-stage fractured horizontal well with tighter clusters considers the non-uniform proppant distribution in fractures in a simple and efficient manner, which can promptly provide favorable guidance for fractured horizontal-well design optimization in tight oil reservoirs.KeywordsTight oil reservoirMulti-stage fracturing with tighter clustersProductivity predictionNon-uniform proppant placementPermeability field functionOptimization design