风城陆相超稠油油砂微压裂扩容机理实验研究

Experimental study on dilation mechanism of micro-fracturing in continental ultra-heavy oil sand reservoir, Fengcheng Oilfield

林伯韬 陈森 潘竟军 金衍 张磊 庞惠文

LIN Botao CHEN Sen PAN Jingjun JIN Yan ZHANG Lei PANG Huiwen

中国石油大学北京石油工程学院 新疆油田工程设计研究院

College of Petroleum Engineering, China University of Petroleum, Beijing 102249, China Oil Production Technology Research Institute, PetroChina Xinjiang Oilfield Company, Karamay, Xinjiang 834000, China

风城陆相超稠油油藏非均质性强且原油黏度高，SAGD 开发普遍存在循环预热周期长的问题。采用微压裂技术可缩短预热周期，由此需要掌握储层在其实施过程中的扩容机理及规律。通过选取风城代表性油砂岩心，进行了岩石力学实验研究，分析了岩心的关键力学参数、剪胀和张性扩容机理。研究发现，风城陆相油砂质地疏松，剪胀角远小于加拿大阿尔伯塔海相油砂，其力学参数和扩容程度受泥质和油质含量的影响；在近井壁地带，围压越小，孔压越大，剪胀扩容量越大；而远井壁地带的剪胀扩容量非常小。张性扩容可通过减小围压和增大孔压2 种方式产生，且塑性强的油砂在张性扩容时产生明显的塑性体应变。综合分析可知，现场微压裂成功的关键在于均匀提压注水并扩大其波及范围。

The ultra-heavy oil reservoir in the Fengcheng Oilfield is characterized by high viscosity and strong heterogeneity, which lead to the long circulating preheating cycle in SAGD (steam assisted gravity drainage) development. The micro-fracturing technology can shorten the preheating cycle. Accordingly, it is necessary to understand the dilation mechanism and rules of reservoirs in the process of micro-fracturing. The representative oil sand core samples were taken from the Fengcheng Oilfield for rock mechanics tests, so as to analyze key mechanical parameters and shear and tensile dilation mechanisms. It is shown that the continental oil sand in the Fengcheng Oilfield is unconsolidated and its dilation angles are much smaller than those of the Alberta marine oil sand in Canada. Furthermore, its mechanical parameters and dilation degree are dependent on mud or bitumen content. The shear dilation near the wellbore increases with the decreasing of confining pressure and the increasing of pore pressure, but that far from the wellbore is tiny. The tensile dilation can be realized by either decreasing confining pressure or increasing pore pressure. The oil sand with strong plasticity can develop apparent plasticity strain during the tensile dilation. It is concluded that the key to the successful in-situ micro-fracturing is to increase the pressure uniformly for water injection and to enlarge its sweep areas.

10.13639/j.odpt.2016.03.016