A Study On Recoverable Reserves Prediction Methods Of Heavy Oil In Liaohe Oilfield

During the process of oilfield development, scientific and appropriate estimation of the recoverable reserves of the reservoirs is the important basis for the evaluation of the oilfield development, dynamic analysis of the oilfield, formulation of the oilfield development and adjustment program, determination of the direction of finding out the potential of the oilfield as well as one of the important evaluation factor of the corporation' s performance.Based on the research results of the forerunners in this field and a lot of indoor paper work, we sorted out problems of current reserve estimation methods and proposed guidelines to solve these problems. Meanwhile, the geologic characteristics of Liaohe heavy oil was described in terms of buried depth, reservoir formation, oil and water relationship, gum content and oil viscosity, respectively. The resourse condition and development situation of Liaohe heavely oil was analysed. The existing classification method of heavy oil was analysed based on Liaohe heavy oil. New classification methods involving buried depth and formation were introduced based on the collection of more than twenty years of experience on Liaohe heavy oil development. This new classification method, based on the geologic and development characteristics of Liaohe heavy oil, combines viscosity, buried depth and formation together instead of only viscosity which is the only factored considered in the original one. Based on these new methods, appropriate development approaches for different reservoirs were proposed.Recoverable reserve is a compound economic index constrained by varies factors. In this paper, for the purpose of comprehensively consider the dynamic and static parameters of heavy oil recoverable reserve, twelve factors influencing heavy oil recoverable reserve were comprehensively discussed. Forheavy oil development involves high cost and investment as well as complex production methods, the influence of technology progress and economic constrain were mainly discussed for the heavy oil recoverable reserve estimation.After careful screening and study, two categories of thirteen types of recoverable reserve calculating method was drawn under the development methods of waterf looding, steam stimulation and steamflooding respectively. Also, combining the economic factor, the concept of economic recoverable reserve was introduced. In the early phase of reservoir development, lacking dynamic data, experience formulas, analogue method and cashflow method were proposed in the study. In the middle and later phase of reservoir development, a lot of dynamic data having been accumulated, water displacement characteristic curve (type A, B, C) method for waterflood development, injection/production relationship method for steam development, widely used Weibull model method, production decline rate method, decline curve method, cashflow method, economic limit watercut limit, economic limit GOR method, economic limit well density and economic production time method were proposed in the study. An integrated calculating system was formed for the estimation of the recoverable reserve in the stages of increasing, stable and decline production of heavy oil development process.Based on the calculation of the recoverable reserves for the four typical blocks including undeveloped block Huan623, waterflooding block Hail, steam stimulating block Qi40 and steamflooding block Shu 1-7-5 respectively, the relative errors of all the methods are basically within the range of 2%. The validity of the methods were furtherly confirmed.