Accumulation Mechanisms and Evolution History of the Giant Puguang Gas Field, Sichuan Basin, China

Abstract

Abstract:Solid bitumens were found throughout the carbonate reservoirs in the Puguang gas field, the largest gas field so far found in marine carbonates in China, confirming that the Puguang gas field evolved from a paleo‐oil reservoir. The fluid conduit system at the time of intensive oil accumulation in the field was reconstructed, and petroleum migration pathways were modeled using a 3‐D model and traced by geochemical parameters. The forward modeling and inversion tracing coincided with each other and both indicated that oils accumulated in the Puguang‐Dongyuezhai structure originated from a generative kitchen to the northwest of the Puguang gas field. The deposition of organic‐rich Upper Permian source rocks dominated by sapropelic organic matter in the Northeast Sichuan Basin, the development of fluid conduit system that was vertically near‐source rock and laterally near‐generative kitchen, and the focusing of oils originated from a large area of the generative kitchen, were the three requirements for the formation of the giant paleo‐oil reservoir from which the giant Puguang gas field evolved. The Puguang gas field had experienced a three‐stage evolution. The post‐accumulation processes, especially the organic‐inorganic interaction in the hydrocarbon‐water‐rock system, had not only profoundly altered the composition and characteristics of the petroleum fluids, but also obviously changed the physicochemical conditions in the reservoir and resulted in complicated precipitation and solution of carbonate minerals.

Primary intergranular pores in oolitic shoal reservoir of lower triassic feixianguan formation, Sichuan Basin, Southwest China: Fundamental for reservoir formation and retention diagenesis

“…When the reservoir receives the last stage gaseous hydrocarbons, there is little activating fluid (Hao et al, 2009). Thus, fluid migration and mass exchange almost cease, and the reservoir diagenetic alteration is weak, leading to reservoir formation finally.…”

“…The oolitic shoal reservoir of the Lower Triassic Feixianguan Formation in the Sichuan basin (Southwest China) has a big success in hydrocarbon (especially gas) exploration recently (Li, 2007), as some giant, large and middle gas fields have been discovered (e.g., the Luojiazhai, Dukouhe, Tieshanpo, Puguang and Longgang fields; Hao et al, 2009;Ma et al, 2008;Zou et al, 2008;Li, 2007;Ma, 2006). Hence, the issue of reservoir origin receives large research attention during recent years for shaping future petroleum exploration strategies and thereby gaining bigger exploration successes (Luo et al, 2008;.…”

“…In China, the success of carbonate exploration shows promising prospects during recent years (especially in the Sichuan and Tarim basins; Li, 2007;Ma, 2006). However, in either China or other countries, carbonate exploration is difficult due to reservoir characterization (Hao et al, 2009;Liu et al, 2008;Luo et al, 2008;Tan et al, 2008;Wang G Z et al, 2008;Xu et al, 2008;Wang Y G et al, 2007;Heydari, 2000). This is because the carbonates are very sensitive to diagenesis, leading to the primary reservoir pores likely being altered during long geological evolution (Huang et al, 2009).…”

Generation of isotopically and compositionally distinct water during thermochemical sulfate reduction (TSR) in carbonate reservoirs: Triassic Feixianguan Formation, Sichuan Basin, China

“…Data from these samples were supplemented by previously published fluid inclusion data from TSR and non-TSR calcite (Hao et al, 2009;Jiang et al, 2014a). Pre-and post-TSR calcite as well as TSR-calcite contained primary, two-phase aqueous inclusions.…”

“…Where TSR-water is the water that is interpreted to be in equilibrium with TSR-calcite at the temperature of growth; BR-water is the water interpreted to be in equilibrium with the host bulk rock at the equivalent temperature of TSR calcite growth.Table 1. Carbon and oxygen isotope, and average value of fluid inclusion salinity and homogenization temperature (Th) of diagenetic calcites from dolomite hosted reservoirs of Feixianguan Formation, Northeast Sichuan Basin: data below detection or no data available; a*: data fromJiang et al, 2014a; b*: data from Li et al, 2012; c* data fromHao et al, 2009; d*: data from Wang et al, 2007; e*: data fromZhu et al, 2005; f*: Wang et al, 2002. …”