Contact Determination, Fluid Typing and Deliverability Estimation in North Caspian Appraisal Wells

Abstract

This paper presents a comprehensive example of wireline formation tester and drillstem tester data that offers insight to compare and contrast the information that can be delivered by these two similar but different technologies. The dataset presented here consists of logs, WFT and DST data from two North Caspian wells penetrating Cretaceous and Jurassic layers. The log data is used to initially predict fluid types and contacts. This is later verified with WFT data. This combined answer is then used to design a well test program to extract maximum data for development planning. Data is also used to defend the booking of reserves before state committees. Difficult reservoir conditions including complex mineralogy and varying and unknown water salinity can make fluid typing and contact determination from wireline logs alone to be problematic. By incorporating WFT downhole fluid analysis data ambiguities in the petrophysical interpretation can be resolved and the results from the continuous log measurements can be calibrated by the sparser WFT dataset. Mobility information from WFT data is also used to calibrate log-derived permeabilities and this is used appropriately plan the DST program. Finally data from the DST program, including rates, fluid types and fluid properties are reconciled with the corresponding WFT data.