_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 229928, “Advancing Saturated Reservoir Evaluation: Gas-Cap Identification and Downhole Constant Composition Expansion Experiment in Volcanic Breccia Formations Through New-Generation Formation Testing, ” by Fang Tao and Yuan Chao, PetroChina, and Fan Zhaoya, SLB, et al. The paper has not been peer-reviewed. _ The Jiamuhe Formation in the Junggar Basin consists of volcanic breccia reservoirs that make fluid typing petrophysically challenging. Traditional methods suggested oil-bearing zones with free water, while drillstring-test (DST) data misinterpreted gas-cap signals as dissolved gas, obscuring gas/oil contacts (GOC). This study integrates new-generation formation-testing (NGFT) technology with advanced petrophysical logging to address these limitations. NGFT Technology The described wireline formation tester (WFT) integrates novel hardware architecture and digital automation. The core innovation is a modular platform centered on a high-efficiency focused radial probe featuring radially arranged guard inlets (44 in. 2) and sample inlets (64 in. 2) within a single packer assembly, delivering a 110-in. 2 total flow area for ultralow-permeability access (less than 0. 01 md/cp). Another core design is a dual-flowline dual-packer system, which can be set flexibly across 1. 82–15-m formations based on reservoir-evaluation requirements. Its dual-flowline configuration maximizes gravitational segregation of wellbore fluids, enabling expedited detection of formation hydrocarbon indications through the upper flowline inlet (Fig. 1). This interfaces with a dual-flowline system connected to two independent, wide-band pump modules capable of 0. 1–100-cm3/s flow rates. Contamination-free sampling is enabled by a sample manager using motor-driven valves that bypass pumps to preserve trace elements and self-sealing pressure/volume/temperature (PVT) bottles with zero-loss transfer. The fluid-analysis module, called the fluid in-situ sample optimizer (FISO), can distinguish individual compositions with an accuracy within 1. 5–3%. Additionally, it can monitor multisensor contamination with an accuracy within 2%, and supports high-value limits for gas/oil/water fractions and gas/oil ratio (GOR), reaching up to 50, 000 scf/bbl. It features a downhole sensor capable of quantifying fluid resistivity accurately and real-time measurement capabilities with laboratory-level accuracy. Formation Testing While Tripping (FTWT) This process uses adjustable dual packers (1. 82–15-m span) to isolate the target openhole zone while activating a dedicated mud-bypass channel above them. During high-volume formation-fluid extraction by the toolstring, rig mud pumps continuously inject fresh mud down the drillpipe/casing annulus. This mud enters the bypass channel to establish an independent circulation loop returning to surface by the choke manifold. Closed blowout preventers and real-time pressure monitoring maintain annular pressure within the safe window. Simultaneously, gravity segregation separates lighter hydrocarbons in the sampling interval, with the upper flowline inlet enabling early hydrocarbon detection. This integrated system decouples formation testing from annular pressure management, enabling safe high-flow-rate deep transient testing while preserving well integrity.
Chris Carpenter (Sun,) studied this question.