Analysis of Decline Curves

Abstract

Since production curtailment for other than engineering reasons is graduallydisappearing, and more and more wells are now producing at capacity and showingdeclining production rates, it was considered timely to present a brief reviewof the development of decline-curve analysis during the past three or fourdecades. Several of the commoner types of decline curves were discussed in detail andthe mathematical relationships between production rate, time, cumulativeproduction and decline percentage for each case were studied. The well-known loss-ratio method was found to be an extremely valuable toolfor statistical analysis and extrapolation of various types of curves. Atentative classification of decline curves, based on their loss ratios, wassuggested. Some new graphical methods were introduced to facilitate estimationof the future life and the future production of producing properties wherecurves are plotted on semilogarithmic paper. To facilitate graphical extrapolation of hyperbolic-type decline curves, aseries of decline charts was proposed, which will make straight-lineextrapolation of both rate-time and rate-cumulative curves possible. Introduction During the period of severe production curtailment, which is now behind us, production-decline curves lost most of their usefulness and popularity inprorated areas because the production rates of all wells, except those in thestripper class, were constant or almost constant. While production-decline curves were thus losing in importance forestimating reserves, an increasing reservoir consciousness and a betterunderstanding of reservoir performance developed among petroleum engineers.This fact, together with intelligent interpretation and use of electric logs, core-analysis data, bottom-hole pressure behavior and physical characteristicsof reservoir fluids, eliminated a considerable part of the guesswork inprevious volumetric methods and put reserve estimates, based on this method, ona sound scientific basis. At the same time, a number of ingenious substituteswere developed for the regular production-decline curve, which made it possibleto obtain an independent check on volumetric estimates in appraisal work, eventhough the production rates were constant. With the now steadily increasing demand for oil to supply the hugerequirements of this global war, proration for reasons other than prevention ofunderground waste is gradually disappearing. More and more wells are, or willbe, producing at capacity or at their optimum rates, as determined by soundengineering practice. T.P. 1758

Production Data Analysis to Predict Production Performance of Horizontal Well in a Hydraulically Fractured CBM Reservoir

“…3) Arps [6]의 생산감퇴곡선법을 통해 예측한 생산량 과 저류층 모델을 통해 취득한 생산량 오차율(production rate error)를 식(9)로 계산한다. Table 4.…”

“…Arps correlations [6] I. 서 론 석탄층 메탄가스의 경우 저류층 내 유체 유동을 지 배하는 자연균열인 탄리의 투과도가 10 md 이하일 때 생산 증대를 위해 수압파쇄(hydraulically fracturing) 를 수행한다 [1].…”

“…서 론 석탄층 메탄가스의 경우 저류층 내 유체 유동을 지 배하는 자연균열인 탄리의 투과도가 10 md 이하일 때 생산 증대를 위해 수압파쇄(hydraulically fracturing) 를 수행한다 [1]. 수압파쇄된 CBM의 생산거동은 전통 적인 가스(conventional gas Table 1과 같은 경험식을 통해 예측할 수 있다 [6]. 모델 격자수는 총 4,107개이고 격자 크기는 100 ft × 100 ft × 5 ft, 석탄층 총 두께는 15 ft로 설정하였다.…”

Economic appraisal of shale gas resources, an example from the Horn River shale gas play, Canada

“…Single well estimated ultimate recovery (EUR) can be estimated directly from historical production data by fitting a decline model (Lee 2012). Among the available models, the Arps model is a well-known model proposed for various conventional reservoirs that has been applied to estimate well EUR for several decades (Arps 1945(Arps , 1956Lee 2012). It has the following form.…”

Prediction of Reservoir Performance Applying Decline Curve Analysis

“…The basic of such an estimate is the assumption that the future behaviour of a well will be governed by whatever trend or mathematical relationship is apparent in its past performance. This assumption puts the extrapolation method on a strictly empirical basis and it must be realized that this may make the results sometimes inferior the more exact volumetric methods [2]. Estimating oil reserves is one of the most important phases of the work of petroleum engineer since the solutions to the Manuscript received November 9, 2012; revised February 14, 2013.…”