Formation,Distribution And Evaluation Of Lithologic And Stratigraphic Traps In The Western Slope,Take Eastern Sag,Liaohe Depresstion,Bohaiwan Basin For An Example

With the deepening exploration of the eastern oil fields in CHINA,Lithologic and stratigraphic reservoir has become the main exploration targets for a long time.The formation,distribution and identification of evaluation of the Lithologic and Stratigraphic traps has become an importante issue of petroleum geology.In the eastern part of China,Continental petroliferous basin of the Mesozoic and the Cenozoic,usually can be divided into three belt:gentle slope,deep sag,steep slopes.The western slope of East Sag of Liaohe Depression is a gentle slope belt with slightly steep terrain,long and narrow form,near to material sources.It has an excellent oil source and reservoir cap configuration,which makes it the favorite area to develop lithologic and stratigraphic oil and gas reservoirs.However,the structure is single,stratigraphic change is complex,facies type changes quickly,so the reservoir of it has the features of small scale and scattered distribution.Exploration progress has been slow for years.To solve these problems above,in the paper,comprehensive study on the structural styles,spatial distribution of sequence stratigraphy,depositional systems.Analyse the conditions of formation and main controlling factors of the Lithologic and Stratigraphic oil and gas reservoirs.Summarizes the distribution law in gentle belt.On the basis of evaluation and prediction,optimized large-scale exploration targets,making the gentle slope a new zone of exploration to succeed.The following achievements and recognition are obtained.1,Establishing three tectonic models of the Western Slope for the first time,which are separately the one with high angle-the faults with same tendency-step-dual slope break,the one with high angle-the faults with contrary tendency-step-single slope break and the one with low angle-override-incline.According to tectonic models and slope break belt differences,the gentle slope belt is divided into 'three sections' on south-north and 'three belts' on east-west.2,Classifying SHAHEJIE group-the target layer in gentle slope belt into two three-order sequences of SHASANDUAN and SHAYIDUAN as well as six system domains,which unifies with the classification of whole East Sag and establishes stratigraphic sequence framework of the Western Slope.3,By core,logging and seismic facies,distinguishing three facies of alluvial fan,fan delta and lake as well as eight subfacies and multi microfacies,simultaneously investigating spatial distribution of sedimentary facies,which indicates that fan delta plain distributary channel and fan delta front underwater branch channel are the most favorite sedimentary facies belts.4,Clearing up the main control factors of forming lithologic and stratigraphic reservoir.1)sequence interface governing the type;2)slope break controlling advantageous position development;3)converging channel dominating distribution range;4)'three lines' which contains Unconformity(erosion surface)scope line of lower and upper subsection of SHASANDUAN,sequence boundary line and mudstone cap rock boundary line of middle subsection of SHASANDUAN and SHAYIDUAN controlling plane partition;5)high-grade reservoir property dominating oiliness.Pointed out that the deposition characteristics control sand body distribution,the fault control hydrocarbon migration in XINKAI slope,while in TIEJIANGLU slope,Palaeogeomorphology control sand body,Reservoir properties control oil and gas?5,Indicating that from good to bad and from bottom to top,the advantageous lithologic and stratigraphic oil and gas reservoirs of the whole slope belt are:the updip lithologic annihilation of middle and lower subsection of SHASANDUAN,stratigraphic unconformity barrier of upper subsection of SHASANDUAN,sandstone lenticular body,stratigraphic overlap,formation heavy oil shield of lower subsection of SHAYIDUAN?6,Use different effective methods to predict the slope of different parts of the stratigraphic traps.The methods contain prediction of reservoir distribution,physical properties,hydrocarbon detection,stratigraphic annihilation lines,mudstone distribution range,oil sealed condition,tec…And identify distribution of good traps.