Decline Curve Analysis for Production Forecast Assurance-A Novel Approach

Thakuria, Chandan (Kuwait Oil Company) | Al-Ghanemi, Mohammad (Kuwait Oil Company) | Bora, Anup (Kuwait Oil Company) | Al-Bahar, Mohammad (Kuwait Oil Company)



Production forecasting always play an important role in decision-making for the corporate management and architecting company’s strategy. In an oil or gas upstream company, the yearly projection of future hydrocarbon production is a routine practice for preparing annual business plan. As sub surface uncertainties pose a huge threat for upstream company, achieving the forecasted crude oil and gas production is challenging in most cases. For national oil companies, having multiple Assets and thousands of wells where reservoirs underpinning different projects at different stages of field development, there arises a need of unified production forecast process that ensures forecast quality. In view of this, Kuwait Oil Company (KOC) initiated a process for improving forecast process adopting best reservoir management practices. In order to make reliable predictions, the engineer must be knoweledgable in variety of techniques to cover the wide range of conditions that are encountered in forecasting process. At the same time, engineer should have enough experience of reservoir behavior to alert the ways in which a given procedure might be changed to yield the most reasonable outcome. In case of using multiple methodology during preparation of forecast, the results obtained by each method and its underlying factor of judgment must be accounted.

The topic intend to share here is focused on developing a quality assurance process for base forecast in a mature reservoir. Base forecast, which also known as no further capital investment case refers to the production forecast that would result from existing wells and facilities. For national oil company’s having huge portfolio of brown reservoirs, base case wedge comprises a significant part of forecast volume. For the base forecast of brown reservoirs, it is always useful to use multiple methodology as applicable and compare their outcome for quality check. A combination plots from multiple methodology helps the field engineer to understand the underlying uncertainty in the forecast. Now a day it is common practice to generate forecast from numerical reservoir simulation model. In contrast, performance base methodology like decline curve analysis (DCA) for brown reservoir shows higher accuracy. However an effort should be made to obtain accurate rate and pressure data to improve the reliability of decline curve analysis (Reference- Fetkovich et al, 1987). A case study has been conducted for base case forecast on a reservoir from the state of Kuwait to identify practical issues and to develop a standard process. This paper is to share this study outcome as well as also to points out some of the uncertainties inherent in the production forecasting and outlines possible solutions. Field examples illustrating some of the challanges in estimating future production rates while using production performance analysis techniques are illustrated here. The need for careful scrutiny of all geological and engineering data is to be consider during forecast preperation. A wokflow has been developed for preparing base forecast and conduct decline curve analysis which lead to enhence reliablity of forecast.