柴达木盆地冷湖地区大地水准面模拟精化计算.pdf

柴达木盆地冷湖地区大地水准面模拟精化计算Simulated and Accurate Computation of the Geoid in lenghu Area of Chaidamu Basin樊德仁陈世云青海石油管理局物探处,甘肃敦煌土里镇,736202.作者:男,1926 年生,高级工程师摘要根据青海石油局物探处在柴达木冷湖昆特依地区进行 GPS 定位提供的高程信息,对该区大地水准面做了模拟精化计算分析,结果表明:该地区大地水准面起伏明显,南北向如LH37LH24 两点距为 43.4km,高程异常值之差为 0.75m,且由北向南逐渐降低;东西向如S205GBG0 两点距离为 26km,高程异常值之差为 1.62m,由西向东逐渐抬高.在获得准确的高程异常情况下,就可得到精度较高的 GPS 高程.同时也说明了用 GPS 高程代替部分水准测量工作是可行的,这就为柴达木盆地大地水准面精化指出了研究方向.用 GPS 精化大地水准是获取精密的大地水准面起伏的一种有效的方法,对地球物理及地球力场模型的建立等科研工作有着重要的意义.主题词/自由词 柴达木盆地,地球物理模型,地球物理异常,精度,高度测量,重力勘探,水准测量中图资料分类法分类号P631前言获得一个区域内精确的大地水准面模型,或者是高分辩的高程异常图,在 GPS 测量中,其目的是为了迅速、准确的求定该区 GPS 定位点的正常高,并为研究该区重力场模型提供重要的参考资料.为了配合昆特依地区地震二维勘探工作,19931994年在该区布设了一定数量的 GPS 定位点.这些定位点包含了丰富的 GPS 高程信息.由于 GPS 定位的高精度,将为精细研究该区大地水准面的变化,提供了条件.然而由于该区 GPS 起算点(约束点),多为三角高程,误差较大,影响高程异常绝对值的精度.所以,只能根据现有资料做一些模拟研究,并通过模拟计算,看出了该区大地水准面在分辩率和精度两个方面的显著改善,说明利用 GPS 高程信息进一步精化柴达木盆地大地水准面的可行性.1精化大地水准面的意义过去,在卫星多普勒定位中,由于柴达木盆地高程异常精度不够,多普勒高程达不到实用要求.这是由于目前我国使用的大地水准面主要是根据莫洛金斯基提出的天文重力水准方法推算得的,在我国西部地区高程异常的实际计算结果精度约为34m,个别地区为56m,在大山区,估计内插高程异常的精度最大可达15m.显然,由于受国家提供的高程异常图精度的制约,使多普勒测定的正常高误差过大,难以实用.为此,我们花费了巨大力量,采用天文重力水准与多普勒水准相结合的方法,开展了对盆地大地水准面的研究,获得了米级精度的高程异常图,初步满足了石油物探工作的需要.但是随着石油物探工作的深入和高精度、高分辩率的需求,高程精度需要提高到分米级才能保证这些勘探工作的精度.如果要进行油田开发或者是油气田勘测,则以厘米级的高程粗度,才能满足工程需要,所以精化柴达木盆地大地水准面势在必行.所谓精化大地水准面,实质上就是精确求定高程异常值或者是大地水准面差距值,以提高高程异常的分辩率和精度.在 GPS 测量中,经过 GPS 网的三维平差后,可获得各点在相应椭球面上的大地高,其精度可达 23ppm.如果在其中一些点上同时进行水准测量,就可得到这些重合点准确的正常高,从而也就求得了这些点的高程异常值.若与其21西安石油学院学报1997 年 3 月第 12 卷第 2 期(J.of Xiq an Petro.Inst.Mar.1997Vol.12No.2)ABSTRACTS OF THE PRESENT ISSUE(JXAPI ISSN1001-5361)Petroleum Geologic Features of Tarim BasinABSTRACT:T arim Basin is a superimposed and composite basin of numerous proto-type basins com-bosed of the Paleozoic cratonic basins and Meso-Cenozoic foreland basins.It has undergone many tectonicmovements and 7 evolutionary stages.T hree major strata of source rocks are found-that is,the Cambrian-Ordovician,Carbonic-Permian and T riassic-Jurassic.Multiple and deep buried rich reservoir rocks are alsodeveloped together with 5 associated reservoir-cap rocks.T he oil,gas and water are complicated in theirproperties and the oil/gas pools are rich and varied in their types.Both oil and gas are rich in this basin andthe gas pools discovered are dominated by condensed gas.T he oil and gas are not only of continental gene-sis but also of marine genesis;the oil pools are mainly of marine genesis,whereas the gas pools are mainlyof continental genesis.Most of the pools are found to be middle to small sized and are characterized by deepburying,lower richness and high productivity.T here are several petroleum systems in the basin and thepools formed in multiple ages;the oil and gas have experienced several times of migration and re-accumula-tion.Still,the distribution of oil and gas in T aim Basin is very complicated and is controlled by many fac-tors,which increases the difficulty of petroleum exploraton.Subject headings/Free words:T arim Basin,petroleum geology,source-reservoir-cap assemblage,oiland gas reservoirZhao Jing-zhou(Xip an Petroleum Institute,Xip an710065.China)JXAPI1997v12n2P8Three Problems about the Petroleum Potential of Luzhou Paleo-Upliftand Jia lingjiang LimestoneAbstract:The control of Luzhou Paleo-uplift over the distribution of gas-bearing layers of Jialingjiang.Limestone was recognized in the late 1950s.But three problem still remain unsolved,i.e.,(1)Howwas Luzhou Paleo-uplift formed?T he answer is:Luzhou Peleo-unplift is now considered as the combinedresult of the compressonal stress by Litou-Qiangtang Indosinian T errane of T ibet structure and the counterstress by Central Guizhou uplift and southern Jia lingjiang Uplift;(2)Why is there no oil and gas in theerosion zone in the upper part of Jialingjiang Limestone?Because there was no Xiangxi coal rocks formedwhen oil and gas migrated to Jialingjiang Limestone;(3)Where is the oil and gas in Jialingjiang Limestone?It is now realized that there used to be a large oil field in Jialingjiang Limestone-Luzhou Paleo-uplift.Butdue to the thickening of the overburden layers and the change of structural configurations,the oil changdinto gas.Then migration and reaccumulation took place and a gas field formed in the newly formed anti-clines.T hus we have the present oil and gas distribution pattern.Subject headings/Free words:hydrocarbon-bearing,oil and gas migration,reservoir formation/Pa-leo-uplift,Jia lingjiang LimestoneA n Zuo-X iang(Petroleum Industry Press,Beijing100011,China)JXAPI1997v12n2P16Simulated and Accurate Computation of the Geoid in Lenghu Area ofChaidamu Basin,Qinghai ProvinceAbstract:Based on the elevation information obtained from GPS survey in kunteyi area of Lenghu,Chaidamu Basin,the authors made simulated and accurate computation and analysis of the geoid of the re-4gion and got significant results.The results show that the geoid undulates distinctively,e.g.the differenceof abnormal elevation values between two south-north going points(LH37-LH24)is 0.75m with their dis-tance being 43.4km and it is getting lower from the north to the south;and the difference of abnormal ele-vation values of another east-west going points(S205-GBGO)is 1.62m with their distance being 26km andit is getting higher from the west to the east.With accurate abnormal elevation value,the GBS elevationwith higher accuracy can be obtained,which proves that the survey of GBS elevation can be used to replacepart of level surveying work.It points out the direction for obtaining accurate geoid of Chaidamu Basin.Subject headings/Free words:Chaidamu Basin,geophysical model,geophysical anomaly,accuracy,elevation surveying,gravity exploration,levelingFan De-ren(Geophysical Exploration Dept,Qinghai Petroleum Administration Bureau,Dunhang,736202,Gansu;China)JXAPI1997v12n2P21Subsidence History Analysis of Bayanhot BasinAbstract:Using backstripping analysis method,the paper made quantitative analysis of subsisence his-tory of Bayanhot Basin.It is held that the subsidence history of Bayanhot Basin includes two uplift stagesand three subsidence stages.The two uplift stages are T riassicEarly Jurassic and Late Cretaceous.T hethree subsidence stages are SilurianPrmian,Middle Jurassic-Early Cretaceous,and Cenozoic.Four typesof basins formed correspondingly.T hey are:a foreland basin(the southern depression belt),a rifted trough(part of Helan rifted trough),a faultsubsided basin and a sag basin during SilurianPermian,Carbonif-erous-Permian,Middle Jurassic-Early Cretaceous and Cenozoic respectinely.In late Paleozoic subsidencemainly occured in the southern depression belt and eastern depression belt.In Jurassic,the southern de-pressin belt rose.T he western depression belt and the eastern depression belt were separated by the middleuplift belt.In Early Cretaceous,the whole basin subsided and became a unitary basin.Subject headings/Free words:Bayanhot,basin,setting,foreland basin,depression/backstrippingLiu xue-f eng et al(Jianghan Petroleum Iastitute,Jingsha,Hubei,434102China)JXAPI1997v.12n.1p25Application of Neural Networks and Expert System in the Inter-pretation of Well TestAbstract:T he paper expounds in detail a new method of identifying the well test interpretation modelby using the expert system and artificial neural networks.First,artificial intelligence was used to identifythe pressure derivative plots of well test model,and a moduler recognition system constructed with expertsystem was set up.Then the artificial neural networks was used to identify the well test interpretationmodel.T his system can identify the well test interpretation model according to the new well test data.Fi-nally the neural networks and expert system were used together for well test interpretation.Practical iden-tification results show that the method is very effective.It can identify incomplete well test data even withnoise.T he identification accuracy is very high compared with other methods.Subject headings/Free words:artificial intelligence,pattern recognition,well test interpretation,neural networksCheng Sui-min et al(Xip an Petroleum Institute,Xip an710065.China)1997v12n2P32,55On the Influence of the Formulation of Ni-P Coating on the Character-istics of Impingemental Corrosion ResistanceAbstract:T he paper studied the behavior of impingemental corrosion resistance of Ni-P coatings of dif-5它方法(如地球重力场模型法)求定的高程异常进行拟合,其精度达到分米级是不成问题的.在国际上,瑞士和奥地利综合利用各种大地测量数据(重力数据、垂线偏差、GPS 水准、数字地型模型、数字密度模型)解算大地水准面,已率先达到厘米级精度.欧洲、美国、英国、德国、加拿大等发达国家和地区的厘米级大地水准面也正在确定之中.我国米级大地水准面研究已提高议事日程.设想到下世纪二十年代,将使我国大地水准面的精度达到厘米级.可见,求定厘米级大地水准面,已经成为国际上大地测量和地学研究的一个重要课题.但目前在柴达木盆地求厘米级精度的大地水准面条件还不具备,主要是缺少高精度的大地测量数据,且在一个区域内进行 GPS 布网时,缺乏对水准高程的联测,因条件的限制,没有开展对盆地内大地水准面的深入研究.这次模拟计算,只是根据冷湖地区GPS 网重合的已知高程点,作了一些必要的探讨.尽管如此,得出的高程异常精度不高,但已清楚地展示了该区高程异常变化趋势的合理性,高程异常图的分辩率也有了相应的提高.更为重要地说明了用 GPS 水准研究区域大地水准面这一方法的正确性.其优点是计算简单,精度高,能一次提供多方面的测量数据而不额外增加工作量.所以,利用GPS 水准精化大地水准面是一种有效途径,同时也是当前获取精密地球重力场信息的一种有效手段.因此,在柴达木盆地大地水准面的研究中,应综合利用盆地大地测量成果,并应在 GPS 网的布设中,从全局出发,有计划地对水准点进行联测,以满足高程异常的成图精度.这样,就会在一个不长的时间内,实现精化柴达木盆地大地水准面的目的.2高程异常值的计算方法利用 GPS 测量资料与水准资料相结合来确定区域性大地水准面的高程或高程异常,是一种简便有效的方法.该方法要求 GPS 观测点具有水准测量资料,且观测点应密度适当,分布较均匀,以控制住高程异常等值线变化趋势为准.计算方法如下:(1)根据 GPS 测量得到的大地高 Hi,以水准测量得到的正常高 hi,高程异常 Ni则为:Ni=Hi-hi(2)GPS 相对定位可以得到两点间精确的大地高差$H;而水准测量又可得两点间的正常高差$hi,故两点间的高程异常差$Ni,故两点间的高程异常差$Ni;为:$Ni=$Hi-$hi(3)如果以 No表示基准点的高程异常值,则可根据(2)式推算任一点的高程异常 Ni:Ni=No+Ni(4)以 GPS 水准求得的高程异常与地球重力场模型或用其它方法确定的高程异常,再进行多项式拟合平差,就可得到最终的高程异常值.(5)把各点求得的最终高程异常值标定在适当比例尺的图面上,就可勾绘出高程异常等值线.6.用适量的水准点对高程异常图的精度进行抽样检查,并估算出高程异常的实用精度.3冷湖地区高程异常的模拟计算在冷湖昆特依地区,我们布设了包括已知高程点在内的50多个 GPS 定位点.由于已知高程点多为三角高程,水准高程仅有3个,这样,必然求定的高程异常精度较差,不能当作正式结果.不过这次模拟计算作为高程异常求定方法的研究和对冷湖地区高程异常变化总趋势的了解,还是有一定的作用.为了使高程异常计算更为接近实际,在模拟计算之前,我们首先对冷湖地区三角高程进行了调查,作出了进行统一归化的改算方案.经与水准高程对比,发现原三角高程存在着0.2m 的系统误差,应予以剔除,使其三角高程与水准高程在系统上尽量保持一致.即便这样剔除系统误差后,三角高程仍然含有较大的高程误差,估计约有0.20.5m 左右.因为三角高程精度是随距离的增大而降低,三角高程规范明确指出,平差后的三等点高程中误差约为0.25m.若考虑到冷湖地区过去测定三角高程只有34测回,其最大高程误差可能达到0.5m 左右.这个误差是不容忽视的,它必将反映到高程异常的计算中,所以出现个别奇异点也是正常的.为了控制该区周界高程异常等值线的走向,我们借用部分GPS 高程,来确定高程异常等值线的走向(见表1).对于出现的个别奇异点只作参考,而不能作为勾绘高程异常等值线的依据.冷湖地区高程异常计算是在 WGS84椭球体上进行(见表2).根据表1、表2计算出的高程异常值进行成图(附图).附图为冷湖地区 WGS84系高程异常图,等值距为0.5m.在勾绘等值线时,由 CHT B 和 YMS6两点高程异常值有点偏大,只作参考,没有当作勾绘等值线的依据.22西安石油学院学报(JXAPI)1997年表1用 GPS 高程计算的周界高程异常值编号点名X(m)Y(m)WGS84H(m)已知高程h(m)高程异常N(m)1LH374298535165446302773.992809.49-35.502LH244256196165546302699.992736.24-36.253LH294269451165622822932.0929689.05-35.964LH214264684165411532708.212744.25-36.045LH344286557165581403021.943057.46-35.526LH324275703165517812768.132803.97-35.84表2冷湖地区高程异常值与计算表编号点名X(m)Y(m)WGS84H(m)已知高程h(m)高程异常N(m)1BSGB4282445165392752778.932814.53-35.602CHTB4258736165535442708.812745.78-36.973CTB2(水)4284184165465562812.562847.88-35.324GBGD4278723165300672750.132786.24-36.115HGB44294292165302092723.612759.17-35.566HQCB4276674165386622733.892769.69-35.807LCT D4272518165455532703.982740.10-36.128PTBA4267307165536022711.102747.39-36.299SQGB(水)4290115165389332741.162776.47-35.3110SZD5(水)4290016165337712997.563032.05-34.4911YM S64285831165295212811.182847.38-36.20附图冷湖地区高程异常图4柴达木盆地冷湖地区 WGS84系高 程异常图的检验对柴达木盆地区冷湖地区 WGS84系高程异常图的精度检验,是采用 WGS84系大地高 H,与在高程异常图上直接按点位读取 N值,并用公式计算正常高 h,即h=H-N.将h 与原 GPS 经过的结束平差后得到的正常高 h 进行比较,求出差值并进行中误差估算(见表3).mh=f2hn=0.61723=0.164m式中:mh 为高程中误差;n 为点数;fh为正常高之差.由表3中看出,在附图中读出的 N值,计算的正常高与原 GPS 平差得到的正常高,最大相差+0.31m,最小为0m.根据23个点估算的高程中误差为0.164m.这个精度说明冷湖地区高程异常模拟计算是成功的,我们认为是比较满意的.同时也证明了这个方法是可行的,如果全部采用水准点,其效果将会更好.5结论(1)GPS 高程是将 GPS 定位技术同几何高程测23樊德仁等:柴达木盆地冷湖地区大地水准面模拟精化计算量技术结合起来用以确定局部高程异常的方法.这种方法不仅原理和计算非常简便,而且精度大大优于常规方法,是精化大地水准面的有效途径.(2)从表2和附图中看出,冷湖昆特依地区大地水准面的起伏非常明显.南北向如 LH37LH24两点间距离为43.4km,高程异常值之差为0.75m,且由北向南逐渐降低;东西向如 S205GBG0两点间距离为26km,高程异常值之差为1.62m,由西向东逐渐抬高,反映了大地水准面与可见地形的相关性.(3)该区高程异常变化的幅度和趋势经与用天文重力水准和多普勒水准拟合勾绘的百万分之一的BJ54系高程异常图比较,其总的形态基本一致,不过就其高程异常值线的分辩率来说,GPS 水准求定的高程异常要精细的多.表3高程异常检验表序号点号HNhhfh1012736.49-35.72762.192762.04+0.152022718.80-35.82754.602754.29+0.313382737.15-35.62772.752772.71+0.044042734.89-35.62770.492770.42+0.075062718.32-35.62753.922753.30+0.026072715.56-35.72751.262751.17+0.097092713.84-35.92749.742749.50+0.248102737.72-35.82773.522773.38+0.149122734.39-35.82770.192770.12+0.0710142732.72-35.92768.622768.51+0.1111152732.79-35.82768.592768.55+0.0412132762.53-35.62798.132798.24-0.1113182714.19-35.82749.992749.99014192700.98-36.12737.082736.33+0.2515172724.69-36.12760.792760.50+0.2916162747.18-35.82782.982782.94+0.0417312821.27-35.92857.172857.18-0.0118302881.30-35.92917.202917.20019282900.42-36.22936.622936.34+0.2820362893.57-35.42928.972929.04-0.0721112802.51-35.42837.912838.13-0.2222082745.38-35.32780.682780.95+0.2723052730.98-35.72766.682766.53+0.15(4)在获得准确的高程异常图的情况下,就可得到精度较高的 GPS 高程.说明用 GPS 高程代替部分水准测量工作是可行的,这对高精度的石油物探工作和解决出地、沼泽等困难地区的高程测量工作将有着重要的应用价值.(5)用 GPS 水准精化大地水准面,可以得到精密的大地水准面起伏,这对地球物理及地球重力场模型的建立等科学研究工作都有着重要意义.参考文献1陶本藻.GPS 水准似大地水准面拟合和正常高计算.测绘通报.1992,(4)2常庆生等.应用 GPS 建立工程控制网的研究.涿州:GPS学术研讨会.19913樊德仁等.青海省柴达盆地大地水准面形状的研究.青海石油管理局地质调查公司,19874宋紫春.精化我国大地水准面的方法与途径.西北地区第七届测绘学术与科技信息交流会资料,1994收稿日期1996-12-27编辑张新宝24西安石油学院学报(JXAPI)1997年