Youqi dizhi yu caishoulu (Jul 2024)
Research progress of shale oil in Jiyang continental faulted basin
Abstract
Shale oil in Jiyang continental faulted basin is a realistic new field for subsequent resource， with enormous exploration potential. It is an important resource base for the sustainable development of Shengli Oilfield. The results of geological research and exploration of shale oil were analyzed in Jiyang continental faulted basin in recent years， and the new progress was systematically reviewed in shale sedimentation， reservoir formation， hydrocarbon generation， shale oil enrichment theory， and supporting fracturing stimulation technologies for Jiyang continental faulted basin. The results show that ① A shale lithofacies classification scheme is proposed based on mineral composition， sedimentary structure， crystallization， and abundance of organic matter ， which can be summarized as “four elements and three ends.” The mechanism of “four paleo-environment factors control shale lithofacies” is revealed， and the orderly “ring-shaped” distribution of shale lithofacies is confirmed. ② The core micro/nano CT scanning， argon ion polishing scanning electron microscopy， FIB-FESEM， nuclear magnetic resonance freeze-thaw， and small-angle X-ray scattering are integrated to form the quantitative characterization technologies of multi-scale shale pore and fracture systems. It is clear that the spaces of the shale reservoir in Jiyang continental faulted basin are divided into both pores and fractures， mainly inorganic pores and fractures. It is revealed that calcite recrystallization， dissolution， and conversion from illite/smectite to illite are the most critical reservoir formation mechanisms， and a reservoir model of shale pore and fracture network is established. ③ The oil content evaluation method of organic-rich shale is developed， which reveals the characteristics of high paleo-productivity， early generation， and early enrichment of organic-rich shale in the saline lake basin. The shale oil resources in Jiyang continental faulted basin are estimated to be more than 1010 t. ④ The shale oil enrichment is controlled by the spatiotemporal coupling of hydrocarbon generation and reservoir formation of bedded/laminated shale， which is characterized by “early formation of saline source rock， inorganic pore， and fracture reservoirs， microscopic source-reservoir integration， and dual coupling enrichment.” ⑤ The comprehensive evaluation system and target selection process for shale oil exploration in continental faulted basins are established， which involves four characteristics and four determinations. ⑥ The fracturing stimulation technologies are developed of “combined fracture network fracturing” and “horizontal well multistage fracturing” suitable for Jiyang continental faulted basin. According to the actual situation of Shengli Oilfield， the exploration idea is proposed of “increasing storage and production in main subsags， exploring new positions in small oil-rich subsags， implementing resources in peripheral small subsags， and taking into account the optimization of mineral rights，” to orderly promote the large-scale increase in storage and production of shale oil in Jiyang continental faulted basin. The relevant achievements and supporting technologies are significant for shale oil exploration and development in similar oilfields.
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