川北阆中-南部地区大安寨段油气藏储层酸压改造技术及实践

Acid Frac Process and Practice in Da'anzhai Oil and Gas Reservoirs of Langzhong-Nanbu Areas of North Sichuan

川北阆中-南部地区大安寨段油气藏成藏模式以"自生自储"为主,总体上属于常温(74～80℃)、高压(原始地层压力系数>1.3)、构造-岩性复合圈闭、薄层状、低丰度、无边(底)水碳酸盐岩裂缝性未饱和油藏或凝析气藏。由于大部分油气井地层压力下降快,地层压力梯度低,产量递减率高,限制了常规酸化压裂等增产措施的推广应用。本文针对大安寨油气藏的地质特征,并结合油气藏开采效果评价,提出了采用胶凝压裂酸化(酸压)技术改造储层的增产措施。通过室内试验得到了凝胶酸TC4-1的配方:20%(HCl)+3.5%(CT1-9)+1.0%(CT1-3)+1.0%(CT1-7)+1.0%(CT5-9)+1.0%(IV-93)。针对不同类型的储层,对酸压工艺进行了优化,并实施了加液氮酸化、压前预处理等配套措施。现场实施效果表明,研制的酸化配方及配套技术具有良好的适应性和显著的增产效果。

Hydrocarbon accumulation of Daanzhai oil and Sichuan is self-generation and self-preservation mainly.It gas reservoir of Langzhong-Nanbu areas of north belongs to structural-lithological trap with normal temperature（74-80℃） and high pressure （initial formation pressure coefficient is more than 1.3）.it is the fissured carbonate non-saturated reservoir or condensate gas reservoir with thin bed,low abundance and non edge（bottom） water.Application and dissemination of conventional acid frac and other stimulation is controlled for rapid decrease of formation pressure ,low formation pressure gradient and high decline rate in most of the oil-gas wells.According to the geological characteristics and the dynamic characteristics of oil and gas production of Daanzhai oil and gas reservoir,the stimulation of acid frac by coagulation is proposed.The formulaof gelled acid is 20%（HCl）＋3.5%（CT1-9）＋1.0%（CT1-3）＋1.0%（CT1-7）＋1.0%（CT5-9）＋1.0%（IV-93） through laboratory experiments.The acid frac process is optimized and matching measures of acid frac added by liquid nitrogen and preprocessing before acid frac are implemented for different types of reservoirs.Field application result indicates that the developed acid formula and matching measures have good availability with obvious simulation effect.