Study On The Fluids Characteristics Of The Marine Strata In The Middle Yangtze Region And It's Connection With Hydrocarbon Preservation

In this paper, the features of marine strata in the middle Yangtze region are that the strata is old, the post-tectonic activity was strong, a number of original reservoir damaged reconstruction happen, the evolution and enrichment of oil and gas is complex. To these features, it starts from the basic work for oil and gas preservation's research focus and difficult in marine strata, and carry out a large number of literature investigation and basic data collection. Regard the petroleum geology theory as guidelines, for example, structural geology, fluid chemistry and fluid compartment etc. , taking structure formation and evolution as the main line, analyze the fluid chemistry - the characteristics of dynamic response in the process of tectonic evolution, restore and reproduce the fluid chemistry - kinetics migration trajectory, construct the marine strata in the middle Yangtze region's current index system of oil and gas fluid compartment to preserve the effectiveness of comprehensive evaluation, analyze the evolution of fluid compartment, definite the main controlling factors of oil and gas preservation system, and forecast the favorable exploration region. The main outcomes and innovation are as follows:(1)In the middle Yangtze region, the tectonic evolution is multi-phase, structure deformation is multi-storey. and it has gone through four phases, such as Caledonian, Hercynian - Tai Au Dalong Indosinian period, as early as a strong deformation of the Yanshan period shift, night Yanshanian - Himalayan extension , early Yanshanian is the main forming period of middle Yangtze region.(2)By using ancient water dynamic field recovery and fluid dynamics simulation technology, according to the multi-phase of tectonic movement in the Yangtze region, the role of deposition and erosion, hydrodynamic conditions, dividing different marine reservoir's underground runoff evolution of the study area into Caledonian period, Hercynian - Indosinian early, late Indo-Chinese - as early as Yanshanian late Yanshanian - Himalayan hydrogeological cycles 2-4, the rehabilitation and reconstruction of the ancient marine reservoir hydrodynamic field. Dynamic field in accordance with reservoir water and groundwater runoff trend convergence characteristics of the study area is conducive to accumulation of oil-gas-water hydrodynamic model: low-power trap-type, low-power semi-trap type, variant steep potential gradient and the platform margin and saddle-shaped, such as streaming potential. Potential field through the fluid analysis of the study area reveals a different structure with different hydrogeological conditions and the complexity of the convergence model to reservoir water, runoff succession, burying the closure conditions and chemical characteristics of water as a rating factor, forecast Yangtze marine areas of favorable reservoir of natural gas gathering section.(3) By using groundwater geochemical factor transformation analysis technique, observing a large number of thin section and identification and statistics the mineral composition and pore filling material, the marine strata in the Yangtze region identified: atmospheric corrosion of fresh water, cave, dissolved joints, muddy and filled to Baiyun combination of fresh dolomite; pyrite, shale discharged ballast water and dolomite recrystallization solution portfolio; tectonic rupture, quartz precipitation, precipitation of pyrite, dolomite shaped, organic composition, such as corrosion. Corresponding to the chemical environment of the water are: quasi-phase with the near-surface evaporation of ultra-salinity aqueous environment; shallow water buried in low-temperature environment; buried deep in - high-temperature brine environment. Reservoir in the anatomy of the hydrodynamic characteristics of field and water chemistry on the basis of the first with the establishment of the causes of the formation water chemistry and mode of sequence evolution.(4) By using fluid geochemical tracer technique, through the comprehensive study about the fluid of carbon, oxygen and strontium isotopes indicate that: the West in most areas of Hunan, Hubei, Cambrian V fluid downward migration Sinian Dengying Formation and upward review of Ordovician reservoir migration, mainly as a result of the analysis of samples formed in the pyrolysis oil, the description under the portfolio of letters separated by insulating fluid is invalidated, under the combination of Western Hunan, Hubei, and the underlying Sinian formation of large-scale oil and gas reservoirs is no longer possible . Western Hubei-Eastern Chongqing Triassic and Permian fluid in the main from the Upper Permian, and the infiltration of surface water by the impact of small, marine portfolio not on the underlying Paleozoic fluid as early as by adding, if the ancient Health sector as exploration for the purpose of layer, under the portfolio has a relatively good preservation conditions. Jianghan Plain area in the early filling fluid, the fluid from the underlying Cambrian, Paleozoic underlying and overlying Triassic connected fluid, early Paleozoic relatively poor preservation conditions; advanced fluid-filled when, as early as the Paleozoic and Mesozoic strata of the fluid are not connected, that is relatively good preservation conditions late. However, Raman analysis of fluid inclusions indicate that the lack of marine strata may be large-scale oil and gas filling. Of fluid chemistry - Kinetics of migration trajectory, analysis of fluid behavior and the trajectory associated with oil and gas into Health System preservation of the integrity and inheritance.(5) According to effective hydrocarbon kitchen, the fluid compartment in middle Yangtze region on marine strata is divided into four major units in vertically: bottom-up, respectivelyⅠ-fluid compartment unit (∈1-Z),Ⅱ- fluid compartment unit (O-∈2),Ⅲ- fluid compartment unit (S) andⅣ- fluid compartment unit (T1-D).(6) Through accumulation dynamic theory to explore the main controlling factors of accumulation. The results show that: to preserve the condition that in the Yangtze area marine hydrocarbon accumulation a key factor, and the tectonic uplift erosion, faulting, fluid to preserve the impact of the succession is the preservation of the three elements of oil and gas. Considering the exposed strata, in particular the extent of the Jurassic cover; late tectonism and fracture strength of the closure; hydro-geological conditions and fluid chemistry - the characteristics of dynamic behavior; fluid compartment of the present pressure and pressure evolution of the ancient ; palaeo-fluid source, cross-layer of palaeo-fluid migration and transport layer the size of the archive of paleo-fluid and fluid quality of the evolution of storage conditions and the causes of various factors such as contact was established in present-day marine strata in the Yangtze area fluid compartment the effectiveness of oil and gas preservation system comprehensive evaluation index system.(7) Regarding the having been established preservation oil and gas preservation efficiency comprehensive evaluation index system of currency fluid compartment system in middle Yangtze marine strata region as standard, combination of fluid compartment controlling factors of oil and gas reservoir analysis, forecast the favorable exploration region in fluid compartment unit. Of which: Jianghan Plain area for a block of unit II-compartment favorable oil and gas exploration zone; Jianghan plain area of zone 2 and Western Hubei-Eastern Chongqing zone 2 for III-compartment unit favorable oil and gas exploration zone; Western Hubei-Eastern Chongqing three blocks for the IV-compartment unit favorable oil and gas exploration zone. Western Hunan, Hubei, no favorable area for exploration.