Identification Method and Effect of Dongjiagang's Alluvial Fan
Cao, Laisheng; Xu, Yingxin; Sun, Lizhi; Pei, Lihong; Yu, Lin; Xie, Liang; Zhu, Hong
The study area is a continuously developed large nose-like structure belt of Paleogene, which located in middle of the west slope of the eastern sag in the Liaohe depression, the early stage of exploration mainly found fault block reservoirs and fault-nose reservoirs in the complex fault terrace, in the south and north of the study area, the exploration degree is relatively high, certain amount of proved reserves have been found in the 3rd member in Shahejie Formation(Es3). The early 3 exploratory wells in Dongjiagang did not drill the reservoir or drilled the thin red layer, so the exploration was once stagnated. We consider that under the control of palaeotopography, multistage of superimposed fan bodies may develop in the study region. In the slope and nose-like structure periclinal parts, there are good conditions for forming lithologic oil reservoir and great potential for exploration.
For a detailed study of the sedimentary characteristics of lower Es3, we applied analysis techniques of Paleo-geomorphic restoring, waveform clustering properties, velocity analysis and amplitude properties to further confirm the fan body's boundary and shape, identify the fan body's physiognomy of southern Dongjiagang, we found that Dongjiagang fan body was more obviously controlled by three ancient valleys, in the lower step of western slope belt, sediment source deposited along the valleys, formed four alluvial fans. In the southern Dongjiagang, Dong 15 well obtained low-yield oil flow, Dong 6 well failed. The result showed the accumulation factors were complex. We established reasonable accumulation mood and identified advantageous reservoir forming assemblage to guide well deployment.
Based on comprehensive analysis, we suggested O58 well in the main channel in Dongjiagang, The well precisely drilled sandstone of Es3 as predicted, and acquired industrial oil flow in the third stage glutenite rock. Deepened the overall understanding of lithologic reservoir accumulation principle, and effectively promoted the lithologic oil gas reservoir exploration in eastern sag. After the research, we achieved three points: (1)Paleo-geomorphology analysis technique is the key to guide fan body prediction; (2)Comprehensively apply multiple geophysical technologies to identify fan body will makes prediction result more reliable; (3)Reasonable accumulation analysis will increase the success ratio of lithologic oil and gas reservoirs exploration.
AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013