Department of Earth Sciences, Quaid-i-Azam University, Islamabad, 45320, Pakistan.
Environ Monit Assess. 2012 Jan;184(1):161-70. doi: 10.1007/s10661-011-1955-4. Epub 2011 Mar 8.
Velocity and density measured in a well are crucial for synthetic seismic generation which is, in turn, a key to interpreting real seismic amplitude in terms of lithology, porosity and fluid content. Investigations made in the water wells usually consist of spontaneous potential, resistivity long and short normal, point resistivity and gamma ray logs. The sonic logs are not available because these are usually run in the wells drilled for hydrocarbons. To generate the synthetic seismograms, sonic and density logs are required, which are useful to precisely mark the lithology contacts and formation tops. An attempt has been made to interpret the subsurface soil of the aquifer system by means of resistivity to seismic inversion. For this purpose, resistivity logs and surface resistivity sounding were used and the resistivity logs were converted to sonic logs whereas surface resistivity sounding data transformed into seismic curves. The converted sonic logs and the surface seismic curves were then used to generate synthetic seismograms. With the utilization of these synthetic seismograms, pseudo-seismic sections have been developed. Subsurface lithologies encountered in wells exhibit different velocities and densities. The reflection patterns were marked by using amplitude standout, character and coherence. These pseudo-seismic sections were later tied to well synthetics and lithologs. In this way, a lithology section was created for the alluvial fill. The cross-section suggested that the eastern portion of the studied area mainly consisted of sandy fill and the western portion constituted clayey part. This can be attributed to the depositional environment by the Indus and the Kabul Rivers.
在井中测量的速度和密度对于合成地震产生至关重要，而合成地震产生又是根据岩性、孔隙度和流体含量解释实际地震振幅的关键。在水井中进行的调查通常包括自然电位、长、短正常电阻率、点电阻率和伽马射线测井。由于这些测井通常用于钻探碳氢化合物的井中，因此无法进行声测井。为了生成合成地震记录，需要声测井和密度测井，这对于精确标记岩性接触和地层顶部非常有用。已经尝试通过电阻率进行地震反演来解释含水层系统的地下土壤。为此，使用了电阻率测井和地面电阻率探测，并将电阻率测井转换为声测井，而地面电阻率探测数据则转换为地震曲线。然后，使用转换后的声测井和地面地震曲线生成合成地震记录。利用这些合成地震记录，开发了伪地震剖面。在井中遇到的地下岩性具有不同的速度和密度。通过使用振幅突出、特征和相干性来标记反射模式。这些伪地震剖面后来与井综合资料和岩性联系起来。通过这种方式，为冲积物创建了一个岩性剖面。该剖面图表明，研究区域的东部主要由沙质填充物组成，而西部则由粘土层组成。这可以归因于印度河和喀布尔河的沉积环境。
