Oil-Water Delineation with a New Formation Tester Module

Abstract

Delineation of oil and water in heterogeneous carbonate formations can be challenging, especially in the presence of low resistivity formations and low mobility zones. Advanced wireline formation testers (WFTs) have traditionally been used in openhole logging for pressure profiles, coupled with downhole fluid analysis (DFA) and sampling for an integrated approach. It is often difficult to obtain well defined oil and water gradients with pressure measurements in tight formations, especially with probe-type tools. Straddle-packer modules are often used to enable flow from low mobility formations. However, the straddle-packer module has operational and differential pressure limitations, as well as a relatively large storage volume in the isolated interval. A field example of oil-water delineation is presented for a low resistivity, heterogeneous carbonate formation. Low formation fluid mobilities required the utilization of a new wireline tester module over the standard probe type tool. A newly designed fluid inlet module with multiple openings was utilized across the low mobility zones for the first time in the industry. This new module avoids issues associated with the interval volume of a dual-element straddle-packer-type tool and provides significantly faster clean up from the formation. In addition, minimized storage results in better Interval Pressure Transient Test data. Faster set/retract operation of this tool and a much higher pressure differential limit are additional advantages over existing dual packer tools. Several station measurements with mobilities of less than 0.1 md/cp were conducted. This allowed oil to be identified across a low resistivity zone, leading to an increased oil column height in the field. Results showed that more accurate oil-water delineation was provided using the new module along with high resolution optical fluid analyzers, identifying mobile oil from low resistivity carbonate zones. In addition, more accurate permeabilities for the tested zones were obtained through pressure transient data analysis.

Flow Modeling and Comparative Analysis for a New Generation of Wireline Formation Tester Modules

“…Across the majority of the parameter space studied (except at high mobility, for which the cleanup time is limited by maximum pump rate constraints), the cleanup time for the 3D radial probe is between 10 and 20 times faster than the conventional probe and between 4 and 8 times faster than the elliptical probe, which can be attributed mainly to its larger drain area and better circumferential connection to the formation. The simulation results are in line with field observations, noting that 3D radial probe cleanup was 15 to 20 times faster than a circular probe (Al Otaibi et al 2012). …”

“…With the current availability of an arsenal of probes having different shapes, focused probes of circular or elongated design, and dual packers, this planning stage has now become a more complex process. The recently introduced 3D radial probe (Al Otaibi et al 2012;Flores de Dios et al 2012) adds another choice for the engineers in planning WFT surveys.…”

Improvements of Sampling and Pressure Measurements with a New Wireline Formation Tester Module in Carbonate Reservoirs

“…Openhole logs do not clearly identify OWC levels as well as fluid type in the low resistivity zones. The decisions on transitional zone saturations and their producibility may often be challenging (Dios 2012, Al Otaibi 2012.…”

Pressure Transient Solutions for Vertically Slotted-Partially Penetrated Vertical Wells in Porous Media

“…Recently Al-Otaibi et al (2012) and Flores de Dios et al (2012) presented two papers on the applications of the slotted-packer module. The first paper dealt with downhole fluid sampling and transient tests in low mobility carbonate formations.…”