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The Sedimentary Facies Characteristics And Favorable Block Prediction In Chang4+5 Member Of Yanchang Formation,ZhenBei-HuanJinag Area

Posted on:2016-03-03Degree:MasterType:Thesis
Country:ChinaCandidate:Y ZhouFull Text:PDF
GTID:2180330461956158Subject:Mineral prospecting and exploration
Abstract/Summary:PDF Full Text Request
Zhenbei-Huanjiang area is located in the southwesternpart of ordos basin, its north boundry is Huanxian, the east is Shangliyuan, the south is Ningxian and the west is Sancha, across the Tianhuan depression and the Shanbei slope, near to the thrust tectonic belts from the west and close to the Weibei upheaval, belongs to the southwest of basin and its area is about 1.1×104km2.Based on integrating the previous research results and through the analysis of the cores, well logging and laboratory data,the author had deeply studied the sediment provenance characteristics, sedimentary microfacies and physical property of Chang 4+5 Member of Yanchang Formation in Zhenbei-Huanjiang area by comprehensively utilizing many theories and means, such as sedimentology, oil and gas geology, reservoir geology and log theories, and provided a base for the searching of favorable block.The follows are the main results of this paper :(1)By similar strata contrast method, the adjacent formation thickness method,sedimentary cycle comparison method, etc using core, logging and logging datas with33 standard Wells as the core and at the same time selecting the eight reference sections, the research conducted the formation contrast and division of small layers for Chang 4+5.the thickness of the Chang 4+51 Member is about 36 m to 63 m, the thickness of the Chang 4+5 Member is about 39 to 60 m.At the same time on the plane distribution features, Chang 4+52 overall is west thick and east thin, Chang 4+51 is east thick and east thin as a whole.(2)Zhenbei-Huanjiang area Chang 4+5’s sediment provenance direction has been made the analysis and the discriminant through the statistics and analysis for sandstone petrology characteristics, light and heavy mineral assemblages and rare earth elements and trace elements such as materials in the research area and combining previous research results, therefore, the sediment provenance characteristics have a preliminary understanding in the study area: sandstone composition in Zhenbei-Huanjiang area is low, lithology are mainly debris feldspathic and feldspathic debris sandstones. The research area is close to sediment provenance direction, there are two main sediment provenance directions, the main sediment provenance is Longxi-Qinling archicontinent in the soutuwest and the second-sediment provenance is Alashan in the northwest and they are all metamorphicrocks, in the midwest tableland of the research area, there may be a mixed, there may be a mixed sediment provenance.( 3) Based on field outcrop, core observation, sedimentary structure, sand thickness and sand/stratigraphic characteristics, the logging response characteristics andgranularity characteristics datas’ statistics and analysis, combining characteristics of regional geological background, sediment provenance features and predecessors’ studying results, there are 3 main sedimentary subfacies called for the delta plain subfacies and delta front subfacies and front delta-coastal and shallow lake subfacies,including Distributary channel, underwater distributary channel, mouth bar, far sand dam, damspace, sand flat, mud flat, mixed flat sedimentary microfacies et.al.(4)According the analysis for typical Wells, section and plane distribution of sedimentary facies characteristics, from the vertical, horizontal, plane distribution regularity of the sedimentary facies in the studied area, development scale has carried on the comprehensive analysis. Zhenbei-Huanjiang area is on the whole in the delta-lake environment, delta front subfacies is the major sedimentary facies, debouch bar microfacies of front subfacies is the main sedimentary microfacies, followed by former delta coastal and shallow lake facies, delta plain subfacies have development,but is less developed.The sandstones are mainly distributed in the delta front mouth bar, distal bar, underwater distributary channel development, the others are in the delta plain subfacies of distributary channel sand flat shore and shallow lake.Mouth bar microfacies is widely distributed in the study area, which has good sandstone physical property, large thickness, good separation and mud content is low. As a result, mouth dam and superimposed debouch bar is the most favorable reservoir facies, far sand dam is a more favorable reservoir microfacies.(5)The logging Sand structure refers to that using logging information c an reflect the characteristics of the sand body’s logging response characteristics.Zhenbei-Huanjiang area main developedⅠfunnel-shaped, followed byⅡfunnel-s haped, mainly distributed in the delta front subfacies, mouth bar, far sand dam is the main corresponding microfacies log structure.Single sand body tired thic kness distribution is one of the important factors affecting the reservoir sand.T he cumulative thickness of the thick sandstone thickness which is greater than5 m in the largest in both Chang 4+51 and Chang 4+52, while its average thick ness is not very big, but its development cycles are relatively higher, it is clos ely related to a large number of development of mouth bar microfacies in the study area.The sandstone cumulative thickness which is biggest is mainly distri buted in the central and northern part of the research area such as Zhen 120,Zhen 41, Zhen 71, Huan 84 around Mubo, Li 76, Xi 63 well and so on in th e delta front, the delta plain subfacies in the western region developed rarely s ingle sand body.(6)In the tested intervals of the research area Chang 4+5, the prolific reservoirgroups are distributed in the river mouth dam sedimentary micro phase, the middle oil groups are also basically distributed in the river mouth dam sedimentary micro phase,low yield oil groups are still in river mouth dam which obtained obvious advantages,followed by the far bar sand mud flat, sand flat; By trying the well capacity type and reservoir thickness relationship analysis shows, thickness of single sand and reservoir capacity have obviously positive correlation.(7) Based on the plane distribution of sedimentary facies characteristics,combined with sand logging structure plane distribution characteristics, the sand thickness and the thickness distribution of single sand etc, along with test data, the article set up the partition prediction table of favorable zones in the study area and have forecasted for Chang 4+5 member in the Zhenbei-Huanjiang area, we have draw the following conclusions:The distribution area of the most favorable zones in Chang4+52 is approximately 1039 km2, accounting for 8.9% of the study area, the zones are mainly distributed in Zhen 141, Zhen 41, Zhen 259, Huan 84 well districts, while also a small range in Huan 98, Li 87, Yuan 88, Mu 33 etc; The distribution area of the most favorable zones in Chang 4+51 is approximately 2089 km2, accounting for17.9% of the study area, the zones are mainly distributed in Zhen 120, Zhen 41-Zhen72, Zhen 79-Zhen 110, Zhen 84 and Huan 97 and Yuancheng area in the northern part.
Keywords/Search Tags:Zhenbei-Huanjiang area, Chang 4+5, Sedimentary microfacies, Sedimentary facies distribution, Favorable block prediction
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