A model of production data analysis for horizontal wells

The production data analysis is one of hot spots of reservoir engineering recently, which combines conventional reservoir engineering analysis and modern well test analysis. Based on the theory of transient porous flow, the analysis provides a mathematical model, which not only reasonably predicts the production decline of oil or gas wells but also effectively evaluates the physical properties of reservoirs. Theoretical charts of Agarwal-Gardner production decline curves and derivative curves for common horizontal wells are presented by solving the transient 3D porous flow in the bounded reservoir. The Agarwal-Gardner curves can be divided into two stages: the derivatives are dispersed in the early transient decline stage and drawn to Arps harmonious decline in the late pseudo-steady state stage. The influence of vertical location of horizontal wells on production decline in the mid-long term is negligible in a homogenous reservoir. A field example illustrates that, given production data, the results in this article can be directly used to evaluate the reservoir characteristics and effectively forecast the long-term productivity for horizontal wells. 生产数据分析是近年来油藏工程的研究热点之一, 它以不稳定渗流理论为基础, 集常规油藏工程分析和现代试井分析之优势形成新的数学模型, 既能合理预测油气井产量递减又能有效评价油气层物性。通过求解封闭地层水平井的三维不定常渗流问题, 可得普通水平井的Agarwal-Gardner型产量递减曲线以及产量递减导数曲线理论图版。分析表明, Agarwal-Gardner型产量递减曲线可以分成2个阶段, 前一段是不稳态递减段, 其导数曲线不归一, 而后一段为拟稳态递减段, 其导数曲线归一, 接近于Arps调和递减趋势; 对于均质储集层, 水平井的垂向位置对中长期产量递减规律影响很弱, 可以忽略。矿场实例说明在已知生产数据的条件下利用该结果可直接评价储集层特性, 并对水平井中长期产能进行有效预测。