Hu, Zhenhua (PetroChina Liaohe Oilfield Company) | Zhang, Shenqin (PetroChina Qinghai Oilfield Company) | Wu, Fangfang (Schlumberger) | Liu, Xunqi (Schlumberger) | Wu, Jinlong (Schlumberger) | Li, Shenzhuan (Schlumberger) | Wang, Yuxi (Schlumberger) | Zhao, Xianran (Schlumberger) | Zhao, Haipeng (Schlumberger)
The igneous reservoir of Shahejie formation in eastern sag of Liaohe depression is characterized by complex geological environment, variable lithology and high heterogeneity. Reservoir evaluation is difficult only based on conventional logs due to complex lithology and pore structures. Effective igneous reservoirs were identified and reservoir controlling factors were analyzed based on effective porosity calculation, pore structure analysis, lithology identification, lithofacies analysis, fracture evaluation and heterogeneity analysis by combing nuclear magnetic resonance data, micro-resistivity image data, conventional logs as well as mud logging data.
Based on our study, the igneous reservoirs in the study area are more related with effective porosity and pore connectivity, and less related with fractures. Good reservoirs are mainly distributed on the top part of explosive facies and effusive facies, where lithologies are mainly Trachyte, volcanic breccia and breccia-bearing tuff. The weathering leaching process is quite important for igneous reservoirs, but the reservoir qulity would not be good if the weathering process is too strong as it will lead to low effective porosity.
The accuracy of igneous reservoir evaluation gets improved a lot by this integrated approach and the conclusion from this study will help to optimize igneous reservoire exploration plan.
Ma, J. (PetroChina Qinghai Oilfield Company) | Yu, H. (PetroChina Qinghai Oilfield Company) | Wang, Y. (PetroChina Qinghai Oilfield Company) | Xian, C. (Schlumberger) | Yang, L. (Schlumberger) | Fu, L. (Schlumberger) | Chen, J. (Schlumberger)
Yingdong oilfield in West China is one of the biggest discoveries recently in china land with probable reserve estimated to be over 100 million tons oil equivalent. This field is small in area coving around 8.1 km2 only. But the oil column is over 400 meters in one of the exploration well and distributed in more than 100 sand zones. Recent seismic work reveals that this reservoir is extremely complex on structure due to the faulty nature. As the consequence of this, significant reservoir compartmentalization is expected and proved by newly drilled appraisal wells. Two wells with only a few hundred meters distance demonstrate completely different hydrocarbon water system. Thus understanding the type of fluid and its distribution becomes the biggest challenge for Yingdong field appraisal and planning the field development in the near future. And testing all these thin zones becomes impractical considering the cost and the time constrains.
A recent project of using Cased-Hole Formation Tester to characterize the fluid type and distribution in three wells in this field was accomplished with great success. 20 zones were carefully selected in three critical wells and tested within one-month time. Besides obtaining high quality fluid samples, the hydrocarbon properties, (GOR, composition, bubble/dew point, etc) are also evaluated in real time with the latest downhole fluid analysis technology. It provides timely input to the current production pilot work. The log interpretation results have been revised in quite a few zones with this formation testing answers also.