Pipeline route selection and ground characterization, Algeria

Abstract

Purpose of the studyA terrain evaluation of a remote area of hyperarid desert in central Algeria was undertaken as part of the frontend engineering design (FEED) studies for a gas field development. The work was part of the identification of suitable route options for a large buried pipeline between the gas fields and the existing pipeline network, some 500 km to the north. The results of the study provided information to support construction costings and preliminary engineering design and construction evaluation of potential geohazards and geotechnical issues, notably trench excavatability and dune mobility, and to help subsequent selection of a specific alignment within the corridor.Techniques usedThe stages involved in the study are summarized in Figure 1, the work formed part of a broader programme of geological studies to characterize ground conditions along a preferred pipeline route. The basis for the preliminary terrain evaluation was a combination of a desk study review and interpretation of a 1:100 000 scale composite (SPOT and Landsat TM) satellite image of the route corridor (approximately 100 km either side of the proposed route). This evaluation was carried out in the UK and was used to identify locations for a limited number of boreholes and trenches. The results from the boreholes and trenches were used, along with a limited ‘ground truthing’ programme in Algeria, to refine the terrain evaluation and provide typical engineering geological and geomorphological characteristics for each terrain unit.The terrain evaluation involved the identification of generic terrain models (i.e. landscape types) each with a characteristic assemblage of terrain units.