Every hydrocarbon discovery is not of commercial scale. Once a reservoir is discovered by drilling an exploration well with encouraging results with presence of hydrocarbons, an extended testing period starts to authenticate the in-place hydrocarbon volumes and deliverable rates and gain more knowledge on reservoir driving mechanism, heterogeneity, geometry, etc. which helps to make field development plan and hence the declaration of commerciality.
OMV Pakistan GmbH. has two discoveries in year 2007, Tajjal and Latif. Tajjal reservoir was discovered in May 2007 in Gambat Exploration License, whereas Latif was discovered in February 2007 in Latif Exploration License. Tajjal is located in south-east of Sawan gas field and Latif is in south-east of Miano gas field, operated by OMV GmbH. Both Tajjal and Latif wells were suspended for almost a year and half until gas pipelines laid from Tajjal and Latif to Sawan CPP and Kandwari CPP respectively for processing the raw gas. Couple of wells drilled in each discovery based on G&G input before start of EWT period as a part of field appraisal plan. In January 2009, extended well test (EWT), an extended testing period started to confirm the in-place volumes and instigate the field development plan for both the discoveries.
EWT is planned to acquire dynamic data for Tajjal & Latif, on average after every 3 months of production a flow after flow test & build-up data have been acquired for estimating reservoir pressure, permeability, type of aquifer & skin factors. Acquired reservoir pressure have substantially used for estimating Gas Initially In Place (GIIP).
Gas in-place estimates are made using EWT data by different techniques; P/Z plots, flowing material balance, analytical model, numerical model and well test evaluations. Results from these methods are reasonably comparable. A resolution will be drawn at the end of EWT phase regarding declaration of commerciality and hence full field development.