IDENTIFICATION OF VERTICAL COMPARTMENTALIZATIONAND COMPOSITIONAL VARIATION BY DOWNHOLE FLUIDANALYSIS; TOWARDS A CONTINUOUS DOWNHOLE FLUID LOG

摘要

Compartmentalization and spatial variations offluid composition are two primary factors thatcause major and expensive differences betweenpredicted and actual performance in the oil field.Fluid compositional variations must beunderstood in order to acquire fluid samplesrepresentative of the reservoir at large, not just oflocal fluid properties. Downhole Fluid Analysis(DFA), a new concept in Wireline logging, isessential to achieve this understanding. Theprohibitive difficulty in the past prior to DFA hasbeen justifying extensive wireline sampleacquisition and lab analysis without a priorievidence of fluid complexities. In this paper,DFA is shown to be the "missing link,"providing the information necessary to optimizethe sampling process and to decide in real timeon where sampling is necessary. A larger numberof DFA stations coupled with several DFAdirectedsampling stations efficiently utilizesfluid analysis resources. DFA is a significantadvance towards the objective of a 'continuousdownhole fluid log.' DFA stations can beincreased in real time in concert with uncoveredfluid complexities without increasing logisticaldemands. In addition, fluid compositionalvariations can be utilized as a tool to identifycompartmentalization because differentcompartments are likely to be filled withdifferent fluids. In particular, DFA is shown toidentify compartmentalization via fluid densityinversions. DFA is a powerful new tooladdressing primary technical concerns forimproving the prediction of production.