隐蔽油藏保存条件研究

影响油藏保存的地质因素主要包括风化剥蚀、差异性抬升和断裂活动.构造油藏由于区域性整体抬升,导致盖层的风化剥蚀,降低了油气的封盖能力.地层油藏的储层和盖层发生了一定程度的倾斜后,相当于其上覆盖层厚度增大,相同的剥蚀量对地层油藏的破坏程度小于构造油藏.岩性透镜体和上倾尖灭油藏多为自生自储型岩性油藏,往往发育在较深的部位,四周被生油岩所包裹,受到构造抬升而遭受剥蚀的程度更弱.对隐蔽油藏而言,差异升降只是造成油藏产状的变化,其中的油气没有因为差异升降而受到破坏.对于构造油藏而言,油气藏形成后,由于差异升降区域倾斜,油气沿抬升了的溢出点外溢,容易造成油藏的破坏.断裂活动可破坏盖层的连续性与完整性,进而影响油藏的保存.当断裂作用只是在一个油藏内部发生,可以使得油气由下部油层向上散失,结果造成油气由一个油层分为多个油层含油.由于岩性油藏大多发育在构造活动较弱的部位,深大断裂一般不发育,断裂活动不会影响到隐蔽油藏的保存.因此,从总体上讲隐蔽油藏的保存条件优于构造油藏.

Study on the preservation condition of subtle reservoirs

Generally,weather denudation,differential uplift and the fault activity may be the main geologic factors of affecting the preservation condition of reservoirs.The regional whole uplift of of structural reservoirs will cause the weather denudating and sealing ability decreasing of its caprock.The damage to stratigraphic reservoirs produced by same denudation thickness is less than that to structural reservoir.The majority of lithological lens and updip pinchout reservoirs are self-generating self-storage lithological reservoirs.They are generally buried at a greater depth,and are enwrapped by oil source rock.Thus their denudation thickness caused by structure uplift is generally less.Differential uplift only causes the change of the occurrence of subtle reservoirs and the oil and gas in them is not destroyed.The differential uplift easily causes the destroy to the structural reservoirs.Fault activity easily destroys the continuity and completeness of caprocks,which will affect the preservation of the reservoirs to hydrocarbon.The fault activity in a reservoir can make hydrocarbon move up from the lower part of the reservoir,which makes the reservoir divide into several oil reservoirs.The fault activity does not affect the preservation of the subtle reservoirs to hydrocarbon because the lithologic reservoirs generally develop in the positions of weaker structural activity.So,generally the preservation condition of subtle reservoirs is superior to that of structural reservoirs.