The oolitic shoal reservoirs of the Lower Triassic Feixianguan Formation carbonates in the Sichuan Basin of southwest China are an important target for gas exploration in the basin.Their occurrence,like other cases wo...The oolitic shoal reservoirs of the Lower Triassic Feixianguan Formation carbonates in the Sichuan Basin of southwest China are an important target for gas exploration in the basin.Their occurrence,like other cases worldwide,can be divided into two locations in general,i.e.,platform interior and platform margin locations.Their differences of reservoir features and origins,however,have not been investigated comprehensively due to different exploration degrees.This issue is addressed in this paper,to provide basic data and information for the basin＇s hydrocarbon exploration and for the study of carbonate platform sedimentology and reservoir geology worldwide.We compared the features of these two types of reservoirs in detail,including the depositional and diagenetic features,pore types and petrophysical features.Based on the comparison,the origin of the reservoirs was further discussed.It is shown that the reservoirs in platform interior and platform margin locations differ significantly.The interior carbonates were deposited in moderate to high energy settings and the dominant lithologic type was limestone,which was weakly compacted and intensely cemented and has undergone meteoric dissolution.Pore types include intragranular dissolution and moldic pores,with low porosities（6%） and low permeabilities（0.1 mD）.By contrast,the platform margin carbonates were deposited in relatively high energy settings and mainly consisted of dolostones with some limestones.The rocks were strongly compacted but incompletely cemented.As a result,some primary intergranular pores were preserved.Both meteoric solution and burial solution have taken place.There are various types of pore spaces including intergranular and intercrystalline solution pores and residual intergranular pores.This type of reservoir generally has better petrophysical properties（9% porosity and 0.1 mD permeability） and pore-throat structures than the interior reservoirs.These differences were influenced by both primary depositional features and secondary diagenesis.For the interior carbonate reservoirs,early meteoric dissolution,weak compaction and strong cementation are important controlling factors.By contrast,the factors controlling the formation of the margin carbonate reservoirs mainly include dolomitization,preservation of primary pores and burial dissolution.展开更多
This paper studied the distribution and utilization status, reasonable exploitation patterns and potential productivity, and sustainable development of marginal lands in the Three Gorge Reservoir Areas. It has been po...This paper studied the distribution and utilization status, reasonable exploitation patterns and potential productivity, and sustainable development of marginal lands in the Three Gorge Reservoir Areas. It has been pointed that problems of the soil fertility degradation, poor productivity in crop lands, natural disasters and environmental deterioration existed in all the exploited marginal lands. In order to maintain the sustainability of the marginal lands, following measure have been proposed: prohibiting cultivation in the crop lands with a slope more than 25°, restoring vegetation in the slope more than 25°, strengthening the basic agricultural construction, establishing the production base of woody feeds and oils, establishing a multi dimensional management model with reasonable structure and optimum function for forestry, agriculture and fishing.展开更多
基金funded by the National Basic Research Development Program(973 project, Grant No. 2012CB214803)PetroChina Youth Innovation Foundation (Grant No. 2011D-5006-0105)Key Subject Construction Project of Sichuan Province, China(Grant No. SZD 0414)
文摘The oolitic shoal reservoirs of the Lower Triassic Feixianguan Formation carbonates in the Sichuan Basin of southwest China are an important target for gas exploration in the basin.Their occurrence,like other cases worldwide,can be divided into two locations in general,i.e.,platform interior and platform margin locations.Their differences of reservoir features and origins,however,have not been investigated comprehensively due to different exploration degrees.This issue is addressed in this paper,to provide basic data and information for the basin＇s hydrocarbon exploration and for the study of carbonate platform sedimentology and reservoir geology worldwide.We compared the features of these two types of reservoirs in detail,including the depositional and diagenetic features,pore types and petrophysical features.Based on the comparison,the origin of the reservoirs was further discussed.It is shown that the reservoirs in platform interior and platform margin locations differ significantly.The interior carbonates were deposited in moderate to high energy settings and the dominant lithologic type was limestone,which was weakly compacted and intensely cemented and has undergone meteoric dissolution.Pore types include intragranular dissolution and moldic pores,with low porosities（6%） and low permeabilities（0.1 mD）.By contrast,the platform margin carbonates were deposited in relatively high energy settings and mainly consisted of dolostones with some limestones.The rocks were strongly compacted but incompletely cemented.As a result,some primary intergranular pores were preserved.Both meteoric solution and burial solution have taken place.There are various types of pore spaces including intergranular and intercrystalline solution pores and residual intergranular pores.This type of reservoir generally has better petrophysical properties（9% porosity and 0.1 mD permeability） and pore-throat structures than the interior reservoirs.These differences were influenced by both primary depositional features and secondary diagenesis.For the interior carbonate reservoirs,early meteoric dissolution,weak compaction and strong cementation are important controlling factors.By contrast,the factors controlling the formation of the margin carbonate reservoirs mainly include dolomitization,preservation of primary pores and burial dissolution.
文摘This paper studied the distribution and utilization status, reasonable exploitation patterns and potential productivity, and sustainable development of marginal lands in the Three Gorge Reservoir Areas. It has been pointed that problems of the soil fertility degradation, poor productivity in crop lands, natural disasters and environmental deterioration existed in all the exploited marginal lands. In order to maintain the sustainability of the marginal lands, following measure have been proposed: prohibiting cultivation in the crop lands with a slope more than 25°, restoring vegetation in the slope more than 25°, strengthening the basic agricultural construction, establishing the production base of woody feeds and oils, establishing a multi dimensional management model with reasonable structure and optimum function for forestry, agriculture and fishing.
