Search

The technique of refracturing is an effective method to solve the rapid decline in oil well production caused by factors such as severe reservoir energy loss and fracture failure after the initial hydraulic fracturing of low-permeability reservoirs. The key to designing refracturing lies in establishing a model for evaluating the potential fracturing layers. Based on the geological characteristics of the low-permeability conglomerate reservoir in the Lower Wuerhe area of the Eig District of the Xinjiang Oilfield, this paper studies the influence of different development approaches on the distribution pattern of remaining oil in the reservoir. A coupled model of remaining oil distribution and the in situ stress field is established and discusses the characteristics of the four-dimensional in situ stress field under different development modes. This paper analyzes the influence of geological factors and well network factors on the distribution of residual oil, and analyzes the influence of various factors, such as reservoir properties and injection and extraction parameters, on ground stress. Based on the residual oil distribution and ground stress changes, an evaluation method for screening potential fractured layers in reservoirs with different development modes (water injection development and depletion development) is developed. [ABSTRACT FROM AUTHOR]

Horizontal well with subdivision cutting fracturing technology is a new technical way to improve the efficient development of shale reservoirs. Subdivision cutting fracturing has the characteristics of stronger inter-fracture interference, more variable parameters and constraints. This fracturing technology has no efficient method to optimize the discrete and continuous fracture parameters integrally. A new automatic integrated optimization algorithm is proposed. The algorithm adopts the SPSA nested binary search algorithm to optimize the discrete and continuous fracture parameters. Considering the flow mechanism of multi-scale media in shale reservoirs, a numerical flow simulation model of subdivision cutting fractured horizontal wells is established. Then, taking the NPV as the objective function, a multi-parameter integrated optimization model is established. Make the method apply to a typical test shale reservoir. The optimization results show that the NPV of the optimum fracture parameter combination is 37.69%–57.36% higher than that of the uniform fracture distribution combination. And the optimum fracture combination presents a spindle-like distribution. This method is applied to an actual shale reservoir in Xinjiang to verify the broad application. The fracture parameter combination of two parallel horizontal wells in the reservoir is optimized. The optimization results show that the NPV has been dramatically improved, with an increasing range of 37.94%–96.84%. And the fractures of two adjacent horizontal wells present zipper staggered distribution. The integrated optimization method of fracture parameters can provide theoretical guidance for hydraulic fracturing design. • A new optimization method of SPSA nested binary search algorithm is proposed to realize the integrated optimization of discrete and continuous fracture parameters. • Considering the flow mechanism of multi-scale media in shale reservoirs, an optimization model with NPV as the objective function is established. • The method has a fast convergence speed and a significant increase in NPV, and the optimized fracture parameters combination is in line with the heterogeneous distribution. [ABSTRACT FROM AUTHOR]