Extract
Green methodologies to test hydrocarbon reservoirs.
INTRODUCTION
The definition and the economic viability of the best development strategy of a hydrocarbon reservoir mainly depend on the quantity and type of fluids, on the productivity of the wells which need to be drilled to bring the fluids to the surface and on the reservoir location. Well tests have been widely used for several decades in the oil industry for estimation of reservoir characteristics such as initial pressure, fluid type, effective permeability and identification of reservoir barriers or boundaries in the formation volume investigated by the test (Coelho et al., 2005). Information collected during well testing usually consists of flow rates, pressure and temperature data, in addition to fluid samples (Woie et al., 2000). In conventional well testing a pressure disturbance is induced in the reservoir by producing the well at subsequent constant fluid rates. Flow rate changes give rise to a sequence of pressure drawdown and buildup periods. The response of the reservoir in terms of pressure at the well is then associated to the imposed production rates and matched with proper analytical or simplified numerical models in order to estimate the sought reservoir properties. According to their duration most of the tests are performed under transient conditions (no boundary of the reservoir are reached by the pressure sink) or under the so called late transient conditions (some but not all of the boundaries are detected). Therefore, the methodology adopted for well test interpretation is generally called pressure transient analysis. There is no single method of testing and sampling that is fit for purpose under every circumstance. The selection of the test type, sequence and duration must be balanced against operational risk, environmental constraints and value derived from affecting early decisions on project appraisal or development. However, conventional well testing methods usually involve surface production of fluid or changing rate at the surface. In exploration and often in appraisal scenarios, surface facilities to store the reservoir fluid are not available and hence the fluid is discharged or flared. Burning hydrocarbons during cleanup and well-testing operations produces significant amounts of emissions that contain unburned hydrocarbons, carbon monoxide and nit...See the full content of this document
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