Schlumberger

Technical Paper: Compartment Identification by Downhole Fluid Analysis

Society: SPWLA
Paper Number: v46n4a5
Presentation Date: 2005
 

Abstract

In the development of deepwater and expensive prospects, it is essential to understand the precise nature of the hydrocarbon fluids in terms of chemical and physical properties, all phase transitions and commingling incompatibilities. The best assurance for accuracy is to perform hydrocarbon analysis at the point of sample acquisition during openhole wireline logging — these agenda are embodied in Downhole Fluid Analysis (DFA. In addition, DFA provides the ability to identify fluid compositional variation and compartmentalization. The DFA logging program can be expanded in real time without logistical constraint, commensurate with discovered fluid and formation complexities. Testing the dynamic response of the fluids during the sample acquisition process provides confirmation of hydrocarbon fluid type and character as well as insight into formation characteristics.

Here, we describe new methods of in-situ hydrocarbon compositional analysis (or DFA by near-infrared spectroscopy. In particular, we establish that known large hydrocarbon fluid density inversions for large vertical intervals, i.e. deep dry gas versus shallow heavy oil, project into subtle density inversions over vertical intervals as small as six feet. Consequently, this paper establishes a new and cost effective method to find compartments - hunting for fluid density inversions by DFA In addition, we describe how two DFA tools at different locations in the sampling tool string coupled with (effective tool separator volumes can be used to ascertain detailed fluid properties. DFA, coupled with wellsite and laboratory analysis, provides the best, most robust hydrocarbon sampling and analysis process.