Great Breakthroughs and Key Technologies in Exploration of Ordovician Deep Buried Hill in Northern Jizhong Depression

Zhang, Yiming (CNPC Huabei Oilfield Company) | Tian, Jianzhang (CNPC Huabei Oilfield Company) | Yang, Dexiang (CNPC Huabei Oilfield Company) | Chen, Shuguang (CNPC Huabei Oilfield Company) | Liu, Xing (CNPC Huabei Oilfield Company) | Hou, Fengxiang (CNPC Huabei Oilfield Company) | Tian, Ran (CNPC Huabei Oilfield Company) | Zhang, Chuanbao (CNPC Huabei Oilfield Company)



The study area is located in the Langgu sag of Northern Jizhong depression, Bohai Bay Basin, East China. In order to achieve exploration breakthrough in deep buried hill, key engineering technologies are developed and used to accurately demonstrate important target identification by recognizing new hydrocarbon accumulation patterns resulting from the analysis of multi-stage structure-controlled trap mechanism and the detailed study of controlling factors over high-quality Ordovician reservoirs based on new high-accuracy 3D seismic data. This study reveals a new evolution mechanism of buried hill controlled by structural superposition, experiencing "the uplift from thrusting in Indo-Chinese to early Yanshan epoch, uplifted block faulting into horsts in middle Yanshan epoch, horsts tilting into belt in Eocene, and belt reversion into trap", and thus puts forward a new mechanism for reservoir forming controlled by a superposition of "dolomite, karsting, and faulting". Three types of reservoir development are identified, including "regional layered pore, local block micropore-fracture, and fracture hole pore layer-block composite", and an accumulation pattern in deep buried hill is constructed, characterized by "efficient hydrocarbon supply from gas-type source rock, predominant migration through fractured surface-nonconformity surface, and stratum- and mass-controlled accumulation", which has guided the 40 years' exploration of Ordovician Yangshuiwu buried hill zone and made a great breakthroughs. Novel relevant exploration technologies have been developed, involving high-accuracy imaging, high-precision well logging identification of hydrocarbon reservoir, ultra-high temperature deep drilling and completion, ultra-high temperature carbonate reservoir stimulation, etc, which solve a worldwide problem that has restricted the exploration of the ultra-high temperature buried hill for many years. These technologies make possible the highest daily production of over 100 m3 oil and 0.5 million m3 gas respectively and sustain a high and stable production for a long term, which guarantee the clean energy supply for Beijing-Tianjin-Hebei region.