Abstract
This paper presents key aspects of a systematic effort for using pressure transient analysis (PTA) as an important building block of full-field reservoir characterization of clastic oil fields in Saudi Arabia. The well-test data for PTA is an important step on the ladder of any integrated reservoir study, aiming at reconciling differences between the static and dynamic models. In this work, a large number of well tests have been analyzed and integrated with other field data. This work highlights the importance of PTA results in refining reservoir descriptions, including permeability modeling and fault characterization in clastic fields. The review of the PTA results, along with other reservoir characterization data of clastic oil fields, has significantly broadened dynamic understanding under a synergistic and multidisciplinary approach.
The subject fields are part of a major fluvial deltaic deposit trend, consisting of stacked oil bearing sandstone reservoirs with inter-bedded shales where the main reservoirs are primarily composed of coarse to fine grained sandstones with thin shale and siltstone intercalations with some lateral barriers (faulting) as captured by seismic data. For the purpose of this study, the fields have been subdivided into several assessment areas with representative transient data to capture the reservoir geology and dynamics. Pressure buildup tests from a number of multi-well groups, generally conducted during single-phase flow (before water breakthrough), have been analyzed by analytical and numerical methods. The analyses of wireline and large, real-time Intelligent Field data have provided key dynamic well parameters, such as permeability-thickness product (kh), productivity index and anisotropy ratio (kv/kh), which are critical input parameters to permeability modeling and history-matching processes. PTA results have also helped in refining reservoir descriptions with events as identifying areas of mobility contrasts, shale body and lateral flow boundaries. Examples of the observed major geological features in the studied fields will be presented.
