ABSTRACT:

Choke management is a crucial process to regulate fluid flow and control downstream system pressure during production, which is of significant importance to evaluate well productivity. In this study, we presented a powerful non-intrusive EDFM (Embedded Discrete Fracture Model) method to investigate the impact of different choke management strategies on well performance. Through the EDFM method, fracture complexities can be considered and captured accurately. We first built a horizontal well with multi-stage hydraulic fractures, where the conductivity can be distributed differently in each hydraulic fracture. Then we used different choke size adjustment methods to determine two distinct pressure drawdown strategies. In this paper, we focus on two representative drawdown scenarios as conservative and aggressive strategies, respectively. By applying the EDFM approach, different levels of fracture closure can be properly modeled in each scenario. Meanwhile, a complex natural fracture network is also considered in this model. Both the fracture closure behavior and complex fracture networks have significant impacts on the production rate and estimated ultimate recovery. Additionally, we presented the visualization of pressure distribution at different times, which provides valuable guidance for the choke management decision. The model in this study can be easily applied to single and multi-well pad developments in other shale gas reservoirs. Our model can be utilized based on field treatment data to match the observed pressure drawdown rate, complex fracture geometry, capture the fracture conductivity change, and fracture closure behavior to estimate the well production.

1. Introduction

Choke management for unconventional reservoirs has been the subject of increasing interest in the oil and gas industry in recent years, which is a key step in regulating fluid flow and controlling downstream system pressure during the initial flowback and production period. The determination of optimal choke size is a complicated task because different pressure drawdown strategies impact the productivity profile directly (Karantinos et al., 2016; Almasoodi et al., 2020). In general, pressure drawdown scenarios can be classified into various levels from conservative to aggressive, diverging from 3.5 to 137.9 kPa/hour (Wilson et al., 2016). Too aggressive pressure drawdown rate leads to strong flowback, which can enhance the production at the initial time, but can result in severe proppant failures leading to fracture closures (Tompkin et al., 2016; Rojas and Lerza, 2018). Conversely, a conservative strategy helps to maintain the hydraulic fracture conductivity while the production rate grows slowly in the early stage (Deen et al., 2015; Bagci and Stolyarov, 2019). Therefore, finding the optimal strategy is a crucial step in the production process. In addition, the existence of natural fractures increases the complexity and uncertainty regarding the well performance (Ezulike et al., 2015; Xu et al., 2015). All these fracture complexities such as complex fracture networks and fracture closure behavior, need an effective and accurate reservoir simulation model to examine their effects on well productivity.

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