{"title":"Delineation of Subsurface Structures Using Gravity Data of the Shallow Offshore, Lamu Basin, Kenya","authors":"D. Ombati, J. Githiri, M. K’Orowe, E. Nyakundi","doi":"10.1155/2022/3024977","DOIUrl":null,"url":null,"abstract":"Lamu Basin is located in South Eastern Kenya and covers about 170 000 km2 both onshore and offshore. Kenya’s Lamu Basin is hitherto underexplored even though there have been notable oil and gas discoveries along the margin of East Africa. This study focuses on the shallow section of the Lamu offshore bounded by 39°E to 43°E by 2°S to 6°S, whereby, unfortunately, some of the wildcat wells turned out to be dry although expensive. Gravity interpretation techniques such as spectral analysis and first horizontal derivative were applied to the reduced gravity data to delineate and model structures to minimize the high investment risks. The gravity data used in this study were sourced from the International Gravity Bureau (BGI) and National Oil Corporation of Kenya (NOCK) digital data courtesy of companies like Woodside Energy, Anadarko Kenya Limited, and Total Exploration and Production companies. The obtained reduced gravity data were gridded to produce the gravity anomaly grids (Free air, Bouguer, and Isostacy), which were consequently drawn into maps. From spectral analysis, depths to shallow sources and deep sources were estimated. These depths were used to set regional and residual separation filters using the Gaussian filter. The first horizontal derivative (FHD) applied to the regional Isostatic gravity anomaly map yielded features that were inferred as intrasediment fractures/faults trending in NW-SE and NE-SW directions. The features like the ridges, troughs, and faults mainly trending in the NW-SE direction are discernable from the regional anomaly map. The developed models show the basement highs and lows with a possibility of anticlinal and synclinal structures and thick sedimentary successions likely to represent good hydrocarbon source kitchens.","PeriodicalId":45602,"journal":{"name":"International Journal of Geophysics","volume":" ","pages":""},"PeriodicalIF":1.0000,"publicationDate":"2022-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"3","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"International Journal of Geophysics","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.1155/2022/3024977","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"GEOCHEMISTRY & GEOPHYSICS","Score":null,"Total":0}
引用次数: 3
Abstract
Lamu Basin is located in South Eastern Kenya and covers about 170 000 km2 both onshore and offshore. Kenya’s Lamu Basin is hitherto underexplored even though there have been notable oil and gas discoveries along the margin of East Africa. This study focuses on the shallow section of the Lamu offshore bounded by 39°E to 43°E by 2°S to 6°S, whereby, unfortunately, some of the wildcat wells turned out to be dry although expensive. Gravity interpretation techniques such as spectral analysis and first horizontal derivative were applied to the reduced gravity data to delineate and model structures to minimize the high investment risks. The gravity data used in this study were sourced from the International Gravity Bureau (BGI) and National Oil Corporation of Kenya (NOCK) digital data courtesy of companies like Woodside Energy, Anadarko Kenya Limited, and Total Exploration and Production companies. The obtained reduced gravity data were gridded to produce the gravity anomaly grids (Free air, Bouguer, and Isostacy), which were consequently drawn into maps. From spectral analysis, depths to shallow sources and deep sources were estimated. These depths were used to set regional and residual separation filters using the Gaussian filter. The first horizontal derivative (FHD) applied to the regional Isostatic gravity anomaly map yielded features that were inferred as intrasediment fractures/faults trending in NW-SE and NE-SW directions. The features like the ridges, troughs, and faults mainly trending in the NW-SE direction are discernable from the regional anomaly map. The developed models show the basement highs and lows with a possibility of anticlinal and synclinal structures and thick sedimentary successions likely to represent good hydrocarbon source kitchens.
拉穆盆地位于肯尼亚东南部,陆地和海上面积约17万平方公里。肯尼亚的拉穆盆地迄今尚未得到充分开发,尽管在东非边缘地区已经发现了引人注目的石油和天然气。这项研究的重点是Lamu海上的浅层区域,该区域位于39°E至43°E之间,2°S至6°S之间,不幸的是,尽管价格昂贵,但一些野井却被证明是干燥的。重力解释技术,如光谱分析和第一次水平导数,应用于简化的重力数据,以描绘和建模结构,以最大限度地降低高投资风险。本研究中使用的重力数据来自国际重力局(BGI)和肯尼亚国家石油公司(NOCK)的数字数据,由Woodside Energy、Anadarko Kenya Limited和Total Exploration and Production公司提供。将得到的简化重力数据进行网格化,生成重力异常网格(Free air、bouger和Isostacy),然后绘制成地图。通过光谱分析,估计了浅源和深源的深度。这些深度被用来使用高斯滤波器设置区域和残余分离滤波器。利用第一次水平导数(FHD)对区域均衡重力异常图进行分析,推断出沉积内断裂/断裂走向为NW-SE和NE-SW方向。在区域异常图上可以看到主要走向北西-东南的脊、槽、断裂等特征。发育的模式显示基底高、基底低,可能存在背斜和向斜构造,沉积层序较厚,可能是良好的烃源灶。
期刊介绍:
International Journal of Geophysics is a peer-reviewed, Open Access journal that publishes original research articles as well as review articles in all areas of theoretical, observational, applied, and computational geophysics.