New Technique for Decline Curve Analysis of Fractured Reservoirs Based On Rate-Normalized Flow Rate Derivative
Authors: Al-Rbeawi Salam , Kadhim Fadhil S. , Owayed Jalal 
Published: April 2024

This manuscript introduces a new decline curve analysis 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). It is easily applied with no limitations or considerations, given to the wellbore or reservoir parameters, except characterizing the flow regimes from the production history.

The concept of the rate-normalized flow rate derivative 1qtxq′ 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. The ultimate recovery (EUR) can also be estimated analytically or graphically using the RNFD. The proposed decline curve analysis technique is validated by applying it to several case studies and compared with the currently used techniques.

The assembly of the RNFD and the numerical model of the flow rate derivative can be considered a promising tool for future performance forecasting. It gives an excellent match with the production history of the case studies examined in this study. The constant behavior of the RNFDs is no longer existed if the production history has undergone the impact of skin factor. For a severe condition of skin factor, the RNFD shows a linear relationship with time instead of the constant value. The transition between flow regimes does not impact the application of the RNFD, i.e., the calculations move very smoothly throughout the flow regime. Smoothing the flow rate data increases the accuracy of the predicted flow rate; however, the proposed technique could work perfectly with the raw production data.

The novelty of the proposed technique is represented by introducing an approach for decline curve analysis that considers the observed flow regimes during the production history. The approach suggests a numerical model for the flow rate derivative and merges it with the RNFD models. A new flow rate model is presented and used to predict future performance. This study introduces new models for the impact of skin factors on production history, especially for early time flow regimes. The proposed approach does not need to know, assume, or calculate wellbore or reservoir parameters; therefore, it can be used for different producing wells from different reservoirs.