四川盆地威远区块典型平台页岩气水平井动态特征及开发建议

位于四川盆地长宁—威远国家级页岩气示范区范围内的威远页岩气田(以下简称威远区块),同一平台上气井的生产动态特征存在着较大的差异,目前对于其页岩气井产气量的主控因素和开发工艺措施的有效性认识尚不明确。为此,以威远区块PT2平台的6口水平井为例,针对气井生产动态存在的差异,从钻遇优质页岩段的长度、水平段轨迹倾向、压裂段长度、改造段数、加砂量及井底积液等方面进行分析,明确了影响威远区块页岩气水平井产气量的主要因素,进而提出了有针对性的开发措施建议。研究结果表明:(1)优质页岩段钻遇长度是气井高产的物质地质保障,水平压裂段长度、改造段数/簇数和加砂量是主要的工程因素;(2)页岩气井生产早期均为带液生产且水气比较大,当产气量低于临界携液流量时,井底积液对产气量和井口压力的影响不容忽视;(3)建议低产井应采用小油管生产(油管内径小于等于62 mm),对于上半支低产井,应及早采取橇装式排水采气工具和措施以释放气井产能,而对于下半支低产井,则应放压生产,防止井底过早积液。

Production performance of and development measures for typical platform horizontal wells in the Weiyuan Shale Gas Field,Sichuan Basin

The Weiyuan Shale Gas Field (hereinafter, "Weiyuan Block" for short) is located in the Changning–Weiyuan National Shale Gas Demonstration Region, Sichuan Basin. In the Weiyuan Block, gas wells even on the same platform are quite different in production performance. And so far, the main factors controlling the gas production rate of shale gas wells in this block and the effectiveness of their development technologies and measures have not been understood clearly. In this paper, 6 horizontal wells on PT2 platform in the Weiyuan Block were taken as the research objects. Aiming at the differences of production performance between these gas wells, this paper analyzes the high-quality shale drilling length, dip direction of horizontal section, length of fracturing interval, number of fracturing stages, sand volume and bottom-hole liquid loading to figure out the main factors affecting the gas production rate of shale-gas horizontal wells. Then, it proposes the targeted development measures and suggestions. And the following research results were obtained. First, high-quality shale drilling length is the material and geological guarantee for the high yield of gas wells, and length of horizontal fracturing interval, number of fracturing stages/clusters and sand volume are the main engineering factors. Second, in the early production stage of shale gas wells, the produced gas contains liquid with higher water–gas ratios. When gas production rate is lower than the critical liquid-carrying flow rate, the effect of bottom-hole liquid loading on gas production rate and wellhead pressure cannot be ignored. Third, it is recommended that small tubing (ID≤62 mm) be applied to low-yield wells. When the upward inclined well has low production, skid-mounted drainage gas recovery tools and measures shall be adopted as early as possible to release gas well productivity. And when the downward inclined well has low production, the production method of decreasing tubing pressure shall be adopted to prevent the early bottom-hole liquid loading.