The Qaidam basin is a complicated basin influenced by multiple tectonic movements. It can be divided into 3 tectonic units including northern block fault belt, western depression and eastern depression. The stratigraphic sequences are well developed in the basin. Except for Archean, Proterozoic, Paleozoic, Meso-Cenozoic are all outcropped, in which marine deposition is developed before Triassic and continental environment is dominated after Jurassic. Source rocks are mainly from Jurassic, Tertiary and Quaternary, which is distributed in northern margin, west and east parts of the basin. The reservoirs are dominated by sandstones and fractures in the basin. There are structural oil pool, stratigraphic oil pool and lithologic oil reservoir. Total hydrocarbon resource is 46.8×108 t in the basin. The proved ratio of oil and gas is 11.81% and 9.31% respectively. Recently, it shows good future for petroleum exploration and development in the basin, but still many geological problem and technological difficult are waiting for solution. However, there is favorable potential for oil and gas exploration and production in Qaidam basin.
3-D seismic exploration in Ma9 area was designed to achieve the geological targets. Due to the constraints of surface conditions,the raw data acquired in this area had a lot of problems,such as various noise,large problem for static correction and reflected signal with low-energy.The conventional seismic data processing is hardly satisfied for high resolution seismic processing. According to the real seismic data characteristics,we analyzed a few problems on the high resolution seismic processing and gave a practical process flow for high resolution processing.Static corrections,noise elimination,wavelet processing,deconvolution,velocity analysis for the targets,optimally iterated stacking and imaging are very important for high resolution seismic processing.With refinement of work flow and selected processing parameters,satisfactory results have been obtained. Signal-to-noise ratio, resolution and dominant frequency of seismic data are improved.
The faults and folds are especially well developed and the structural patterns are complex and multiplex in southern margin of the Junggar basin.On basis of analysis of the distribution and formation mechanism of faults and folds in the area,it is suggested that the fold system can be divided into four parts:the NW-NWW trend fold system;the approximately EW trend fold system;the NE trend fold system and the piedmont fold system in north margin of Bogda mountain.And the development of faults is inhomogeneous with obvious regional difference. The fault system also can be divided into four parts including Tianshan piedmont belt,north Bogda piedmont belt,EW conjoining belt and Chaiwobao depression. Southern margin of the Junggar Basin underwent multi-epochs of tectonic movements such as Hercynian,Indosinian,Yanshan and Himalayan,and these movements resulted in different tectonic systems.The structure architecture of southern margin of the Junggar Basin is characterized by zonation in NS trend and fault blocks in EW direction because of the tectonic superimposition.
The Tarim basin is one of well developed area of Cretaceous with the interbedded continental and marine sequence and the continental sequence.There are various well-preserved fossils in the sequence. On basis of previous study result,the timing and belonging of lithostratigraphic units of the Cretaceous sequence in southwestern and northern Tarim basin was analyzed.Time of some important stratigraphic units was studied in detail and was correlated with that in neighbouring area. The Cretaceous stratigraphic framework was established in the Tarim Basin and a tentative time correlation system of Cretaceous lithstratigraphic units in southwestern and northern Tarim basin was in action.
An easy method of denudation recovery,"trend analysis",based on the former achievements,combined with the facts in Junggar basin,is put forward in this paper. Recovery of the denudation of middle and upper Jurassic in the inner Junggar basin is tried with this method. The results will direct oil and gas exploration in this area.
Several kinds of biomarker of the source rocks in the Member 1 of Yanchang Formation, Upper Triassic in Shaanbei area have been detected by GC and GC/MS. The source and maturity of organic matter were investigated by using a lot of geochemical indicators .The result indicated that the source of organic matter in the deep and shallow lake are aquatic plants and animals, and in delta are mainly terrene plants. The organic matters are mature according to the index of isomerization of sterane and terpane. The results are important in studying the distribution and hydrocarbon generation capacity of the source rocks of the Member 1 of Yanchang Formation, Upper Triassic in Shanbei area.
Based on the study of stratigraphy and petrology of outcrop and well sections, using the single factor analysis and comprehensive mapping method,palaeogeography maps of Tarim basin during five epochs of Ordovician period were compiled. Evolvement of paleogeographical situation of different epochs can be used to estimate the change of sea level. From Lianghekou-Honghuayuan epoch to Baota epoch,sea level was rising;and during the Linxiang-Wufeng epoch,marine regression was happened. Based on the analyses of 87Sr/86Sr,δ13C and microelements evolution during Ordovician,the fluctuation of sea level in the period in Tabei area were resumed.It is estimated that sea depths descend twice during Lianghekou-Honghuayuan epoch and once during the middle of Dawan-Guniutan epoch.
Reefs are favorable for enrichment of hydrocarbon and some ore reserves due to the well-developed pore and cavity. Current information indicates that the highest yield of oil fields in the world almost is in organic reefs. However,in the actual exploration and production,there are many subsurface structural forms confused easily with organic reefs,which may results in great economic loss. With the development of geophysical exploration and the advance of practice experience,it is easier to discriminate the organic reefs from other similar buildups such as volcanic lithoherm. Based on current relative documents and references,the history and the prospects for exploration of organic reefs is introduced. Some attention is paid to how to distinguish organic reefs from other similar buildups by their different seismic characteristics.
Base on the systematic study of the hydrocarbon accumulation conditions and the analysis of the typical oil and gas reservoirs,the distribution of oil and gas in the four foreland basins of central-western China can be summed up as follows.Firstly,oil and gas is mainly distributed in foreland thrust belt,keeping away from orogen.Structural reservoirs are mainly concentrated in the thrust belt and forebulge belt,and non-structural reservoirs such as lithologic and stratigraphic reservoirs are mainly developed in fore-deep and front slope belt.Secondly,the found oil and gas mainly circle around the hydrocarbon kitchen,and the scale of reservoirs was increased following the increase of the hydrocarbon discharge intensity of source rocks.Thirdly,hydrocarbon is mainly distributed in the fine reservoir-caprock assemblages under regional caprocks,for example,most of hydrocarbon reservoirs in Kuqa foreland basin are discovered in the reservoirs below the Lower Tertiary gypsum mudstone caprock.The delta and the shore-shallow lake depositional systems are favorable facies for hydrocarbon accumulation.Fourthly,the oil and gas reservoirs are mainly distributed in the areas controlled by effective carrier system,and the traps nearby the dominant pathway are most benefit for oil and gas accumulation.Lastly,the hydrocarbon accumulation in the foreland basins of central-western China is characterized by multi-stage accumulations and late adjustment.The Late Himalayan oregeny was the major stage of adjustment,with a lot of secondary reservoirs as Dawanqi and Yiqikelike reservoirs formed.
柴达木盆地北缘大柴旦区块的平顶山-黄泥滩构造带、大柴旦断陷带和欧南断陷带油气成藏条件各不相同.绿梁山南翼的平顶山-黄泥滩构造带中、下侏罗统暗色泥岩发育,古近-新近系和中生界冲积扇、河流-泛滥平原相沉积中砂泥岩储层广布,背斜构造发育,且形成时间早,有利于寻找构造油气藏;绿梁山北翼的大柴旦断陷带侏罗系暗色泥岩也很发育,烃源条件良好,但断裂作用强,构造破碎,以寻找小断块、断鼻和岩性地层圈闭油气藏为宜;东部欧南断陷带侏罗系烃源岩发育,侏罗系、白垩系及古近-新近系碎屑岩储层发育,并且周边地区也获得工业油流或见不同程度的油气显示,但缺少构造圈闭,应以寻找岩性和地层圈闭油气藏为主.
针对塔河油田碳酸岩岩溶洞穴裂缝型油藏特点,从水平井的部署、设计、参数优化、开发效果及利用水平井挖潜等开发实践方面,总结了水平井和侧钻水平井在本油藏的应用情况后得出:利用水平井开发并非塔河碳酸盐岩油藏开发唯一的选择和最佳选择;水平井相对于直井开发的优越性在该油藏并未得到充分体现;因此认为在储层预测、流体识别和缝洞系统定量描述满足不了水平井设计要求时,不易大规模实施水平井开发,尤其是对于复杂特殊性油藏更是如此.因此建议水平井开发部署因暂缓,首先实施"直井+侧钻"的现实可行做法,再度尝试部署斜井.
Lithologic reservoir is a hot spot of exploration at present. The Upper Jurassic Suining Formation gas pool recently discovered in Luodai area on the eastern slope of the western Sichuan depression is a lithologic reservoir. A comprehensive analysis of the reservoiring pattern of Suining Formation gas pool in Luodai field shows that it is a secondary gas pool sourced from the Lower Jurassic and Upper Triassic. The reservoirs are tight sand, with an average porosity of 4. 74% and permeability of 0. 417×10-3 μm2. Delta front underwater distributary channel and mouth bar are the favorable reservoir micro-facies. The extensive superimposed sandbodies constitute reservoir space for large scale accumulation of gas in the Suining Formation, which is facilitated by the paleoslopes. Favorable facies belt is a key factor for a high gas rate well. The discovery of Suining Formation gas pool in Luodai area has changed the previous wisdom that the Suining Formation can only act as a regional seal in the western Sichuan depression. Its production potential has drawn the attentions of geologists.
A number of intra-continental foreland basins were developed in central and west China since the Meso-Cenozoic. The sedimentation and development of this kind of basin was controlled by intra-plate tectonic stress in lithosphere in accordance with the deep geophysic data. In terms of relationship of among tectonics, basins and sedimentation in lithosphere, basin was formed by combining actions of "intra-continental subduction" of mantle, "structural disintegration" of crust and thermal isostatic movement of mantle. The orogenic belt on the basinal margin was as the main provenance, and fluvial, deltaic and lacustrine sedimentation was developed under suitable climatic condition. Therefore, it is very important in study of controls of tectonics of lithosphere on basinal sedimentation.
The fracturing effect is usually reflected by valid period.But the influence factors are too many to determine the forecast model.BP neural network can consider multiple variable factors,and self-organizes the parameters that may influence the valid period,establishes the comprehensive accurate model on valid period eventually.The example shows that the prediction model can forecast the valid period more accurately and rapidly.The method provided by this paper has wide application foreground.
Gas source of the Ordos basin comes mainly from the alternate marine-continental coal-bearing stratum of Shanxi and Taiyuan Formations. The Upper Shihezi Formation has a vast thick layer of mud with very good sealing property.At present,some gas pools have been found in the Shiqianfeng Formation above the Upper Shihezi Formation in the eastern Ordos basin.These gas pools have low pressure and pressure coefficient,light gas composition, low gas saturation and low volumetric, and small gas pool scale. Formation mechanism of the secondary gas pools has been put into attention by many explorers. In this paper, inclusion homogeneity temperature is used, together with terrestrial heat evolution history, to analyze the in-pouring time of gases. Homogeneity temperature spans very wide in the Shanxi and Shihezi Formations (80 ℃～160-,200～70 Ma),showing that the gas in-pouring has experienced many times. Homogeneity temperature spans very narrow in the Shiqianfeng Formation(160-, 100～70 Ma),showing that the gas in-pouring has experienced only once, accordant to structure movement during the late Cretaceous period.
Abundant gas resources are contained in the Permian at the western Ordos basin, and investigation of its reservoir occurence is very important for gas exploration. Guided under the thoughtway of the dynamical reservoir geology, the influence of dynamical function on reservoir evolution is analyzed. It was showed that the Permian sandstones were in their early diagenetic stage during tectonic movement of foreland basin which taken place at the Late Triassic. Under the control of sedimentary dynamical process, structural dynamical process, thermal dynamical process and fluid dynamical process, there was a marginal dissolution compartment in the coaly formation in the studying area,and the evolution of Permian sandstones in different tectonic setting is quite different.
In order to improve the understanding to the oil and gas reservoirs in west frontier of SINOPEC,some characteristics has been summarized from the logging presentation,the function of well logging in finding oil and gas reservoir,thin reservoir,low porosity reservoir and the test result of reservoirs,with some examples had been showed.It is showed that integrated analysis of well logging data,logging presentation,the data of experiment,the test result and engineering data is essential for effectively find oil and gas reservoirs,and the function of well logging in finding oil and gas reservoir is important at the same time.Moreover,don't look down on thin reservoir and low porosity reservoir.
Based on the correlation of GS and biomarker between the Cretaceous oil-bearing core of well HC-1 and the source rocks of the well and adjacent area,it was indicated that the deep grey mudstone developed in the lower part of Liwaxia formation was the only matured source rocks in the Cretaceous in the area. The maturity of crude oil is equivalent to that of mudstone, and they shows certain affinity. In the future exploration, attention should be paid to evaluation of the source rocks.
After 6 years of systematic research,the Nanjing Research Institute of Petroleum Physical Exploration has made great progress in the DIPOG system centered by seismic technique. The research thought trains and characteristics are introduced in this paper.
Based on the information of surface outcrop and deep geophysical data of lithosphere profile along the Hexizoulang region(Golmud-Ejin),the integrated geological and geophysical interpretation was made and the deep structure,architecture and thermal regimes in the region were revealed.Furthermore,the relationship between the deep tectonic movement and thermal activity in lithosphere and the hydrocarbon migration in the Mesozoic-Cenozoic basins was discussed.
