重磁电一体化勘探技术在柴达木盆地西部复杂地区的应用

以柴达木盆地西部为代表的复杂山地地区,是我国重要的油气资源勘探远景区。由于受复杂地表条件、复杂地质构造双重因素的影响,油气勘探难度大。首次采用三维重磁电综合地球物理勘探方法在柴达木盆地西部复杂地区开展油气勘探攻关。三维大地电磁资料采集以面元为单位代替传统排列式采集,重力资料采集利用正交高密度基点网法提高采集精度。针对研究区的三维重磁电资料,采用三维预处理技术压制地形及局部不均匀体的影响,利用钻井资料作为约束,进行三维反演处理,获得了研究区地层电阻率、密度的空间分布。结合钻井、地震等资料对研究区开展了综合石油地质解释评价,提出了有利的勘探目标。

基于时频电磁法的富有机质页岩层系勘探进一步研究

为了发挥非地震勘探技术成本低、效率高的优势,检验电法勘探技术在页岩气勘探中的有效性,分别于2011、2012年对分布于四川盆地南部的志留系龙马溪组-奥陶系五峰组、寒武系牛蹄塘组两套典型富有机质页岩层系进行了时频电磁法(Time-Frequency Electromagnetic Method,TFEM)页岩气勘探试验。岩石样本研究表明,这两套页岩层系具有较为明显的低密度、低磁化率、高极化率、高TOC、相对高电阻率,即"两低、两高、一相对高"的物性特征。2012年进行的面积时频电磁法勘探试验结果与2011年完成的二维时频电磁法勘探试验结果均表明,试验区分布的志留系龙马溪组-奥陶系五峰组层系具有高极化率与相对高电阻率异常分布特征。以时频电磁法勘探获取的高极化率异常为主,通过多参数评价,预测了试验区两套目标层系的TOC高值分布区。

Prediction study of hydrocarbon reservoir based on time-frequency domain electromagnetic technique taking Ili Basin as an example

The time-frequency domain electromagnetic(TFEM)sounding technique can directly detect oil and gas characteristics through anomalies in resistivity and polarizability.In recent years,it has made some breakthroughs in hydrocarbon detection.TFEM was applied to predict the petroliferous property of the Ili Basin.In accordance with the geological structure characteristics of the study area,a two-dimensional layered medium model was constructed and forward modeling was performed.We used the forward-modeling results to guide fi eld construction and ensure the quality of the fi eld data collection.We used the model inversion results to identify and distinguish the resolution of the geoelectric information and provide a reliable basis for data processing.On the basis of our results,key technologies such as 2D resistivity tomography imaging inversion and polarimetric constrained inversion were developed,and we obtained abundant geological and geophysical information.The characteristics of the TFEM anomalies of the hydrocarbon reservoirs in the Ili Basin were summarized through an analysis of the electrical logging data in the study area.Moreover,the oil-gas properties of the Permian and Triassic layers were predicted,and the next favorable exploration targets were optimized.

Experiments on excitation and data processing of low-frequency vibroseis in permafrost area of the tibetan plateau

Few seismic exploration work was carried out in Tibetan Plateau due to the characteristics of alpine hypoxia and harsh environmental protection needs.Complex near surface geological conditions,especially the signal shielding and static correction of permafrost make the quality of seismic data is not ideal,the signal to noise ratio(SNR)is low,and deep target horizon imaging is difficult.These data cannot provide high quality information for oil and gas geological survey and structural sedimentary research in the area.To solve the issue of seismic exploration in Tibetan Plateau,this test used low frequency vibroseis wide-line and high-density acquisition scheme.In view of the actual situation of the study area,the terrain,the source and the diff erent observation system were simulated,and the processing technique was adopted to improve the quality of seismic data.Low-frequency components with a minimum of 1.5Hz of vibroseis ensure the deep geological target imaging quality in the area,the seismic profi le wave group is clear,and the SNR is relatively high,which can meet the needs of oil and gas exploration.Seismic data can provide the support for the development of oil and gas survey in the Tibet plateau.

四川盆地深层海相页岩气赋存机理与勘探潜力

深层—超深层页岩气是四川盆地天然气增储上产的战略接替领域。基于志留系页岩气的大量勘探开发实践、实验测试资料和前瞻性研究成果,探讨了深层海相页岩气的赋存状态与聚集机制,指出了四川盆地深层页岩气的有利勘探区。页岩的纳米孔喉系统决定了其内部聚集的天然气呈现吸附态,主要以单分子层在微孔—介孔中吸附聚集。页岩吸附气量除受控于孔、缝的比表面积,还受TOC含量、温度、压力和含水性的影响。深层高温条件下,页岩储层的最大吸附气量较低,随着温度降低页岩的吸附能力增强,最大吸附气量也逐渐增加。页岩气在深层超压条件下主要以游离气赋存,呈超临界状态高密度聚集,游离气含量受储集空间及孔喉结构、埋藏深度、地层温度和压力、超临界流体性质以及页岩含水性等诸多因素综合影响。在抬升过程中,因构造改造的强度、时间和方式不同,页岩气的赋存相态转化及散失机制不同。其中,抬升幅度小且改造强度弱时,页岩气层仍保持深层“游离气为主,超压富气”的特性;抬升至中—浅层时,受断裂开启、剥蚀露头和页岩自封闭性降低等游离气散失机制影响,页岩气层的含气量和游离气量降低、吸附气占比增加,因此,远离剥蚀区、大断裂带的深埋藏区是深层页岩气的最有利富集区。四川盆地内部构造相对稳定,深层海相页岩气普遍保持着“早期滞留,超压富气”的成藏特征,优选宜宾—泸州地区、綦江—涪陵地区、永川—大足地区和垫江—梁平地区为有利勘探区。

温度压力耦合作用下的页岩气吸附分子模拟——以鄂西地区下寒武统为例

为考察随地层温度和压力变化,页岩气吸附性质变化规律,采用分子模拟技术,构建黏土矿物—干酪根复合分子模型,揭示在温度压力耦合作用下页岩气吸附特征及微观机理。研究结果显示,页岩气在干酪根、干酪根—伊利石复合模型、伊利石狭缝孔吸附能力依次降低,且均为较弱的物理吸附;页岩气在狭缝孔中的吸附量随着地质埋深的增加而增加,但当狭缝孔道被水分子占据后页岩气吸附量不再呈现出明显的增加趋势;在压力较低的情况下,气体的吸附能力由压力决定,在压力较高的情况下,气体的吸附能力由温度控制,在超高压且含水率较高的条件下,页岩气会以溶解气的方式赋存于含水页岩之中。模拟结果进一步表明,页岩气在干酪根—伊利石复合模型中的吸附主要以游离气为主,吸附气次之,其中吸附气含量占比达20.55%~38.82%。研究结果对分析随地层演化页岩气吸附性质变化规律及含气性预测具有一定的实践意义。