Tight Gas Reservoirs; Challenges for Appraisal and Development, Case History from Abu Dhabi Oil Company for Onshore Operations (ADCO) Fields

摘要

ADCO operates the oil and gas reservoirs/fields in onshore Abu Dhabi. Tight gas reservoirs are thin bedded, laminated and heterogonous carbonate reservoirs. Testing of the tight gas reservoirs in vertical wells was not justifying the completion, hence the production, mostly for economic reasons due to low and non-sustainable rate. Recently, ADCO commenced a campaign to appraise the tight gas reservoirs in the onshore operating fields. The first trial was commenced in Jan 2010. In which, the Lower Thamama; with five (5) sub-layers, thin-bedded, laminated and heterogeneous gas reservoirs were appraised. The drilling within a six (6) feet thick interval of sub-layer for almost 1000’ was really an operational challenge prior to dive the well across the dense (stylolitic) interval to drill the second thin sub-layer. The well trajectory was adapted to appraise as much sub-layers as possible aiming benefiting maximizing the reservoir contact per drain- hole. The production results from the first appraisal well encouraged the team to set a development plan. The well-planning by targeting different sub-layers minimized the well interference and improved the draining areas per well. The 3D seismic interpretation, core data, log analysis and formation evaluation in addition to test data from vertical wells were the basis for the 3D reservoir modeling in order to understand the lateral heterogeneity of the reservoir hence planning the well geometry to geosteering within the developed reservoir areas. Imaging While Drilling is a real-time tool that afforded excellent well-placement practices. ADCO is enthusiastic to aggressively tackle the tight reservoir issues to produce bypassed hydrocarbons. The challenges are huge however the expectations are immense.