摘要
产量递减分析,就是当油气田(井)进入递减阶段以后,寻求产量变化规律,并进行未来产量预测。通过对递减规律的深刻认识,分析出影响产量递减的主要因素,进一步采取有效的措施来减缓产量递减,以提高最终采收率,做到科学合理开采。目前国外对油气田产量递减规律的研究已有上百年的历史,首先,R.Aronld和R.Anderson最早提出了产量递减的概念,给出了计算递减曲线的数学方法。然后,Arps基于递减比对递减规律进行了归纳,给出了产量—时间方程和产量—累计产量方程,把递减规律的研究上升到量化水平。最后,国外许多学者对递减规律做了大量深入研究,如Fetkovich首次提出了现代产量递减曲线分析方法,Palacio和Blasingame提出了等液量递减曲线分析法,Agarwal和Gardner提出的A-G产量递减分析方法等。总之,国外已具有相当成熟的理论方法,在实际应用中也取得了很好的效果。国内对产量递减的研究起步较晚,主要是针对递减类型和递减方程的描述研究,总的来说并没有超出Arps递减的理论框架。同时,采用的方法手段也多种多样,主要包括扩展Arps方法,标准图版法,曲线拟合法,最优化方法,数值模拟方法等等,总体上针对油藏递减分析的研究较多,而针对气藏,特别是低渗致密气藏递减规律的研究相对较少。
本文通过对国内外相关研究成果的综合分析,提出了A-B-F产量递减模型。该模型是以Arps传统产量递减分析模型为基础,将Blasingame现代产量递减曲线分析方法与Fetkovich标准曲线图版拟合方法相结合,不仅兼具了传统产量递减分析方法和现代产量递减分析方法的优势,而且在产量预测、地层参数求取、地质储量预测方面具有预测精度高,计算简便等特点。
论文首先根据该气藏的实际情况,将所有单井划分为六类:无改造措施高产井、有改造措施高产井、无改造措施中产井、有改造措施中产井、无改造措施低产井和有改造措施低产井;然后利用A-B-F产量递减模型对每种类型的单井进行产量递减规律分析;再后根据单井产量递减规律,结合气藏的地质特征与开发特征,分析了影响JP1、JP2气藏单井产量递减的主要因素;最后从气藏实际出发提出了减缓产量递减的技术对策。这些成果认识对JP1、JP2气藏的科学合理开发将具有积极意义。
论文取得的成果及认识如下:
(1)对新场气田JP1、JP2气藏已有资料的收集、整理与分析知两个气藏具类似的地质特征和开发特征具体表现为:①有较强的非均质性;②初期产量递减快、后期产量递减缓慢,基本无稳产期;③单井控制储量小;④气藏产水量小,井筒积液普遍;⑤井间连通性较差,压力下降不均衡;⑥采出程度低、差异较大。
(2)利用A-B-F产量递减模型在新场气田JP1、JP2气藏单井产量递减分析中取得了较好的效果。主要体现在:单井产量递减规律与实际情况相符,所求地层参数与试井解释结果一致,动态产量预测与实际产量拟合较好。
(3)新场气田JP1、JP2气藏单井产量递减规律分析。通过统计发现JP1、JP2气藏大多数单井符合双曲线递减,少部分单井符合指数递减,没有调和递减的单井出现。总体上都呈现出高产井递减指数小,产量递减快;低产井递减指数大,产量递减较慢;中产井递减指数间于两者之间的特征。
(4)通过对JP1、JP2气藏典型井及单井产量递减规律对比分析,结合气藏地质及开采动态特征具体分析影响单井产量递减的主要因素。这些因素表现在以下几个方面:改造措施对产量递减的影响,气井产水对产量递减的影响,其他开发因素对产量递减的影响,地质因素对产量递减的影响。
(5)针对JP1、JP2气藏单井产量递减的主要影响因素,提出了减缓气藏单井产量递减的开发技术对策。由于新场JP1、JP2气藏在地质特征和开发特征上的特殊性,需从气藏描述、压裂改造措施、气井排水措施、布井方式、气井配产及采气速度等方面制定相应对策。
总之,利用A-B-F产量递减模型来研究新场气田JP1、JP2低渗致密气藏单井产量递减规律,获得较好的效果。该方法不仅兼具了传统产量递减分析方法和现代产量递减分析方法的优势,而且在产量预测、地层参数求取、地质储量预测方面具有预测精度高,计算简便等特点。因此该方法可用于分析同类气藏单井产量递减规律,以进一步指导气藏开采技术政策的制定和调整,最终达到提高采收率,增加经济效益的目的。
The analysis of production decline is that seeking the law of production changes when oil and gas field (wells) went into the decline stage, and predicting future production. By The law of production decline deep understanding of the impact of the main factors of production decline, and further take effective measures to slow the production decline to increase ultimate recovery, so that scientific and rational exploitation. The law of production decline oil and gas fields have been studied hundred years abroad, first of all, R. Aronld and R. Anderson proposed the concept of production decline firstly, and given the mathematical method of calculating decline curves. Then, Arps classified on the law of production decline which based on decreasing ratio, and given output-time equation and output-cumulative production equation, to study the law of diminishing the level rose to quantify. Finally, many foreign scholars have done a lot in-depth study on the law of diminishing, for example, Fetkovich the first time proposed that modern methods of production decline curve, Palacio and Blasingame proposed the equivalent liquid decline curve analysis, later Agarwal and Gardner proposed A-G production decline analysis. In short, the foreign has a fairly mature theory method, and has made a good effect in practical application. In domestic the study of decline of production started late, mainly aimed at decreasing the type and description of research on the decline equation, but does not exceed the Arps decline of the theoretical framework generally. Also a variety of methods and means used, including expansion of Arps method, standard plate method, curve fitting, optimization approach, numerical simulation, etc. In short, the analysis of reservoir decline more, but for the gas reservoirs, particularly low permeability tight gas reservoirs of the law of diminishing relatively small.
Based on the results of a comprehensive domestic and international research analysis, the A-B-F model of production decline has been taken out. The model is based on Arps traditional production decline model, the Blasingame modern production decline curve analysis method and Fetkovich standard curve fitting combination plate, Not only the production decline possesses both traditional methods and modern methods of production decline of the advantages, but also having been the character of high precision on prediction, simplicity calculation in the production forecast, obtaining formation parameters, geological reserves forecasts.
Firstly according to the actual situation of the gas reservoir, all single wells are divided into six categories:no reform measures high-yield wells, reform measures high-yield wells, no reform measures medium-yield wells, reform measures medium-yield wells, no reform measures low-yield wells and reform measures low-yield wells; Then taking use of the model of A-B-F production decline to analysis the production decline law for each type of single well; then under the single well production decline law, combined gas reservoir geological characteristics and the development characteristics,sum up the main impact factors of JP1, JP2 gas reservoir single well production decline; the final, gas reservoir slow production decline proposed technical countermeasures is raised up. Understanding on these results will be of positive significance on JP1, JP2 gas reservoirs scientific and reasonable development.
Knowledge and results of the Paper are as follows:
(1) Analysis about JP1, JP2 gas reservoir data been collection, collation and of the two known these gas reservoirs are with similar geological and development characteristics:①strong heterogeneity;②initial production decline rapidly, post production decline slowly, almost no stabilization period;③small single well controlled reserves small;④gas reservoirs are with little water, well bore fluid is general;⑤poor connectivity between wells, the pressure drop is not balanced;⑥low level of recovery, quite different.
(2) A-B-F production decline model used in the well production decline analysis obtains good results to the new gas field JP1, JP2 gas reservoirs. Mainly reflected in the law of single well production decline is in line with the actual situation, the formation parameters are consistent with the well test interpretation, and dynamic performance prediction is well fit with the actual yield.
(3) Analysis about the law of diminishing of JP1, JP2 gas reservoir. Found by statistical JP1, JP2 single well gas reservoir is most accord with hyperbolic decline, a small number of single well exponential decline, there does not reconcile decline of the single well. Emerged the overall high-yield wells decline index is small, the production decline rapidly; low-yield wells decreasing indices is large, production decline slowly; the medium-yield wells are between with the two features.
(4) On JP1, JP2 gas reservoirs and the law of comparative analysis of single well production decline, combination of reservoir geology and exploitation of dynamic characteristics to the specific analysis on the single well production decline of the main factors。These factors shown in the following areas:reform measures on the impact of production decline, gas well production water on the impact of production decline, other development factors on the production decline and the geological factors on the impact of production decline.
(5) For the major factors affecting the Single well production decline of JP1, JP2 gas reservoir, the technical countermeasures to slow the development are proposed. As the JP1, JP2 gas reservoirs have the special features in the geological characteristics and development, countermeasures on the gas reservoir description, fracturing measures, gas drainage measures, well spacing, gas well production and gas recovery with speed to develop should be draw up.
In short, making use of A-B-F production decline model to study the JP1, JP2 low permeability tight gas reservoirs single well production decline law, better results are obtained. It not only combines the advantage of traditional and modern production decline analysis method, but also presents high precision and simplicity calculation in yield prediction, obtaining formation parameters, geological reserves forecasts predict. So the method can be used to analyze the diminishing law of the same gas reservoirs well yield, thereby can further guide technology policy formulation and adjustment of the gas reservoir, and ultimately achieving enhanced oil recovery, increasing economic efficiency.
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