Control Factor On Form Oil Pool Of Complex Fault Block Oilfield

Complicated faulted nose﹑fault block field in fault basin are widely spread inEastern China in the mid-Cenozoic, inasmuch as the complexity of its geologicalcondition results to the difficulties of exploration and development. With thedevelopment of oil exploration theory study and application of new explorationtechnologies, especially to the completion of the complicated fault block reservoir'sdetailed prospecting program, have enhanced the ability to resolve the complicatedsub-surface structures and predicting accuracy of complicated fault block wherehydrocarbon pools are found.However the complex ruptures and the complex sediment depositional patterns,largely increases the study difficulties of oil pool forming mechanism and hydrocarbonaccumulation rules. These factors have restrained the successes recorded in oilexploration of complicated fault block.In order to solve pool forming theory issues and practical problems, to draw clearpictures of controlling factors for pool forming in complicated fault block, tosummarize rules of oil pool forming in the place where fault nose and fault block areon the slope of faulted basin, this thesis has taken the BIYANG depression as a casestudy, taking the research thoughtway of system theory together with dynamic andstatic combination researching method, guided with modern geology theory, applyingsequence stratigraphy, the latest geophysical technology, oil-reservoir geology methodand all kinds of computerized prediction technology, standing in the position of entiredepression, to have a integrated research in structure evolution, sedimentarymicro-facies, reservoir characteristics, oil pool forming rules.Summarize the character of complicated fault block oilfield, establish thehydrocarbon accumulation mode of complicated fault block pool, and anatomize thestructure forming mechanism of northern slope zone. Analyzing from oil generation,reservoir, caprock, trap, migration pathway and storing, conclude the controllingfactors of pool forming with characteristic of complicated fault block, combined withpractice, draw conclusion of realizing method of complicated fault block. Thepublication has stated geological conclusions and realisations amongst which are:1. From structure,sediment evolution and its spatio-temporal configuration,analyze the forming mechanisms,faulting tectonism episode period,stress-fieldevolution,sediment evolution,controlling factor, anatomized the mechanisms of nosestructure on northern slope: It has been realized that transtension stress-field formed byassociated action—strike-slip of the marginal rupture in fault basin, result in thedevelopment of series nose structure, together with angle of conjunction control thenose structure and spread style of sand body: obtuse angle～wide, acute angle～narrow;The upper (over-burden) sediment difference compaction increases the scaleof nose structure.2. Brought forward the joint transtension-stress of margin-fault cut nose structurewhere formed the different trap styles;fault from different tectonic movement andfaulting activities have different controlling function: older faults is active continually,the downthrow and upthrow(fault interfaces) grind and extruded, which leads toexcellent sealing ability, while the younger fault are non-sealing and control petroleummigration-accumulation, and have the function of reallocation to the early formedpools;fault provides the channels(pathway) for petroleum migration in the function offlow and seep at active tectonic stage, whenas it will enclose oil and gas to formreservoir at stillness phase;The relativity of fault-sealing ability at the fault planecontrol oil column height.3. To probe the mechanism of oil migration and accumulation, the preponderantpath, and rules of dynamic evolvement by making full use of the developing theoriesof oil reservoir and systemic methods of petroleum to study the dominated factors ofreservoir forming and time-space relations of element on forming condition ofreservoir and process of forming on northern slope zone.To summarize the rules oil pool forming of northern slope, to establish thehydrocarbon accumulation model of the complicated fault-nose as below: inheriteddeveloping fault-nose slope is the point to zone of petroleum migration, detailedly,nose-structure accumulates hydrocarbon, faults adjust and control the reservoirforming, the cutting relations between nose-structure and faults dominate the modelsof petroleum migration and accumulation. There are two models: one is wing-piece(along cutting), another is axes-line (cross cutting). Petroleum migration keep to twomain categories rules: ①as a whole, petroleum migrates from south to north and fromdeep to shallow levels, locally migrates firstly to axes of nose. ②mainly, petroleummigrates along sand body with good connectivity to its root part, in the case ofencountering faults, it begins accumulate or adjust migration.4. To form a systemic petroleum exploration technology aim at complicated smallfault block on shallow-stratum. To uncover the reservoir property of complicated smallfault block on shallow-stratum and the tectonic character of northern complicatedcluster fault block by utilizing the updated construction analytic technologies. A totalof four profitable exploration target fields (Wangji-Xingzhuang, Gucheng, Yanglou andFuwan) were evaluated;Two profitable formations (shallower formation and lowerpart of H3) were discovered. To add more succeed resources to the eastern old oilfield.The technology accomplished the goal of exploring and developing this kind of oilfield in a short time and low cost, and will be useful to guide oil field exploring anddeveloping with similar complicated fault block.