页岩气水平井生产规律

随着我国页岩气开发工作的逐步深入和开发规模的不断加大,适时开展气井生产数据分析、评价已投产井生产规律是评价阶段开发效果和制订下一步开发部署的依据和保障。为此,通过分析北美地区6个页岩气开发区块和我国国家级页岩气示范区长宁—威远区块、昭通区块的页岩气水平井生产数据,采用双曲—指数混合递减模型建立不同区块的归一化产量递减曲线,探讨了页岩气井初始产量的变化趋势和产量递减规律,并建立了页岩气水平井估算最终开采量(EUR)的快速评价方法。研究结果表明:①在开发初期页岩气水平井平均初始产量均呈现逐年上升的趋势,而初始产量分布则存在着差异,而后,气井平均初始产量变化呈平台式,后期则呈逐年下降的趋势;②双曲—指数递减模型应用于中国和北美地区页岩气水平井的产量递减分析具有较好的适应性,同一区块不同批次的气井产量递减规律相似;③长宁区块前3年产量递减比例依次为55%、38%和33%,与北美地区Fayetteville区块接近,威远区块生产初期产量递减比例依次为63%、 46%和37%,明显高于北美地区5个区块;④气井EUR与第1年累计产气量(Q_1)正相关,一般为Q_1的2～5倍,Woodford区块气井EUR/Q_1最高,长宁区块与Barnett、Eagle Ford、Fayetteville和Haynesville区块相当,而威远区块则相对较低。

Production laws of shale-gas horizontal wells

With the gradual advancement of shale gas development and the continuous increase of development scale in China, analyzing the production data of gas wells appropriately and evaluating the production laws of in-service wells provides the basis and guarantee for the evaluation of interim development effects and the formulation of next development schemes. In this paper, the production data of the shale gas horizontal wells in six shale gas development blocks of North America and China's national shale gas demonstration areas (including Changning–Weiyuan Block and Zhaotong Block) were analyzed, and the normalized production decline curves were established for different blocks by virtue of the hyperbolic–exponential hybrid decline model. Then, the variation trends of initial production and decline rates of shale gas wells were discussed. Finally, a fast evaluation method for the estimated ultimate reserve (EUR) of shale gas horizontal well was developed. And the following research results were obtained. First, in the early stage of development, the average initial production of shale gas horizontal wells presents an increasing trend year after year, but the distribution of the initial production is different. Then, the average initial production of gas wells varies in a platform-like mode. And in the later stage, a trend of decline year after year occurs. Second, the hyperbolic–exponential hybrid decline model is better applicable to the production decline analysis of shale gas horizontal wells in China and North America. The gas wells put into production in different years in the same block are similar in production decline laws. Third, the production decrement of the Changning Block in the first three years is 55%, 38% and 33% respectively, which are close to that of Fayetteville Block in North America. Whereas, the production decrement of Weiyuan Block in the initial stage of production is 63%, 46% and 37% respectively, which are much higher than that of the 5 blocks in the North America. Fourth, the EUR of gas wells is positively correlated with the cumulative production of the first year (Q1), and it is generally 2–5 times the Q1. As for the of gas wells, the Woodford Block is the highest, the Changning Block is equivalent to Barnett, Eagle Ford, Fayetteville and Haynesville Blocks, and the Weiyuan Block is relatively lower.