New approach for decline curve analysis of unconventional fractured reservoirs: Rate-normalized flow rate derivative concept

Abstract

This manuscript introduces a new decline curve analysis (DCA) technique to analyze and predict the potentials of hydraulically fractured unconventional resources. The new approach relies on the rate-normalized flow rate derivative (RNFD) concept. It uses the significant constant behavior of the RNFD that identifies the power-law type flow regime models of fractured reservoirs. This technique merges the RNFD with a new numerical model for the flow rate derivative (flow rate noise-reducing derivative model). The concept of the RNFD $\left[\frac{1}{q}\left(tx{q}^{\prime }\right)\right]$ is developed based on the power-law type analytical models of the flow regimes that can be characterized from the production history of gas or oil-producing wells. The production rate, cumulative production, and the calculated RNFDs from the production history are used for this purpose. The constant RNFD values and the flow rate derivative's numerical model can be used to simulate the production history or predict future performance. The impact of the skin factor is introduced to the approach by developing new RNFD models that could replace the constant pattern of RNFD when this impact does not exist. For a severe condition of skin factor, the RNFD shows a linear relationship with time instead of the constant value. The proposed approach gives an excellent match with the production history of the case studies examined in this study. The transition between flow regimes does not impact the application of the RNFD, i.e., the calculations move very smoothly throughout the flow regime. The novelty of the proposed technique is represented by introducing an approach for the DCA that considers the observed flow regimes during the production history and the impact of the skin factor. The approach proposes new numerical flow rate and cumulative production models to predict future performance as well as new models for estimating the impact of skin factors on production history, especially for early time flow regimes.