致密油藏压裂后衰竭开采单井可采储量预测新方法

A novel method for predicting recoverable reserves of single well through depletion-drive development after fracturing in tight oil reservoirs

由于致密油藏的地质特征、渗流特征、开发特征及生产特征均有别于常规油藏,因此亟待建立适应于致密油藏压裂水平井开发的生产动态分析及可采储量预测方法。以致密油藏压裂后的衰竭生产特征为基础,根据油藏工程基本理论,应用物质平衡与动态分析方法提出了一种简便且广泛适用的致密油藏压裂后衰竭开采单井可采储量预测新方法。研究结果表明,在单井最小含水率一定的条件下,单井可采储量采出程度与含水率变化有关。通过绘制关系图版,发现投产初期含水率降低速度较快,随着可采储量采出程度的不断上升,含水率下降速度逐渐减缓,且单井可采储量采出程度及含水率均随最小含水率的减小而降低。当可采储量采出程度为1时,生产井含水率降至最小含水率。以准噶尔盆地吉木萨尔凹陷芦草沟组X区块的12口致密油井为例,应用该方法分别预测了单井可采储量,计算了可采储量采出程度,并通过对比其中2口生产井的理论图版曲线与实际生产数据,验证了该预测方法的可靠性及准确性。此外,基于提出的理论与方法,预测了2口实例井的生产动态,并分别得到了累积产油量、累积产水量与含水率之间的生产动态关系曲线,用以评估油井当前生产状态并预测生产趋势。

Because the geological characteristics,seepage characteristics,development characteristics and production characteristics of tight reservoirs are different from those of conventional reservoirs,it is urgent to establish the production performance analysis methods and the prediction methods of recoverable reserves applicable for the development of fractured horizontal wells in tight oil reservoirs.Based on the characteristics of depletion-drive development of tight reservoirs after fracturing and the basic theory of reservoir engineering,using material balance and dynamic analysis methods,this paper proposes a novel,simple and widely applicable prediction method for recoverable reserves of single well in tight reservoirs through depletion-drive development after fracturing.The study results show that under certain minimum water cut of single well,the recovery factor of recoverable reserves of single well is related to the change in water cut.By drawing the relationship chart,it is found that the water cut decreases rapidly in the initial stage of production.With the continuous increase of recovery factor,the decline rate of water cut gradually slows down,and the recovery factor of recoverable reserves and water cut of single well decrease with the minimum water cut decreasing.When the recovery factor of recoverable reserves is 1,the water cut of the production well drops to the minimum value.Taking 12 oil wells in a tight oil block X of Lucaogou Formation in Jimsar sag,Junggar Basin as examples,using the proposed method,this paper predicts the recoverable reserves of single well,calculates the recovery factor of recoverable reserves,and verifies the reliability and accuracy of the prediction method by comparing the theoretical chart curves and actual production data of 2 production wells of them.In addition,based on the proposed theory and method,this paper also predicts the production performance of these two case wells,and obtains the relationship curves of production performance between cumulative oil production,cumulative water production and water cut,respectively,so as to evaluate the current production state of oil wells and predict production trends.