Tester (BASIC-RCT™).
COSL’s “Basic Reservoir Characteristic Tester” or “BASIC-RCT” is a third generation product of the formation tester family, characterized by its pump through function. BASIC RCT is a compact, convenient, safe and efficient tool. It can replace in part Drill Stem Testing (DST) operations in order to save rig time. BASIC RCT provides economical and reliable solutions to formation evaluation for oilfield exploration and engineering, representing a good means to reduce cost while solving difficult technical problems. BASIC RCT can be run on any service company logging unit, requiring only winch, cable head and depth measurement. All services, telemetry, gamma ray recording, test recording (digital, numerical listing, screen and printer graphics) are provided in real time. Tool configurations are shown in Figure 1.14. For latest specifications, the reader should refer to the manufacturer’s updates.
Functions
Measuring formation pressure accurately
Taking multi-samples of formation fluids
Taking large samples
Pumping through contaminated formation fluids
Monitoring formation fluid properties in real time.
Flowing formation fluids at controlled rates
Pumping through in reverse
Making quick well site sampler transfer
Providing real time and reliable data for analyzing permeability and formation damage
Structure
The BASIC RCT is a combination of surface system and downhole tools. The surface system includes the Acquisition and Data Process software, PC and DC control panel, and AC power supply. The downhole tools include the upper electronics section, mechanical/hydraulic section, sensor section, lower electronics section with a standard configuration, and also include the 2 × 520 cc large sampler with optional configuration (see Figures 1.15 and 1.16).
Figure 1.14. Tool string configurations.
Figure 1.15. Tool architecture.
Figure 1.16. Tool and surface system.
Figure 1.17. Pressure drawdown curve (left) and fluid contact curve (right).
1.2.3 Enhancing and enabling technologies.
While we principally focus on pressure transient analysis in this volume, a number of enabling technologies contribute to the operational success of formation testers in general, and in particular the robustness of the tools mentioned in Sections 1.2.1 and 1.2.2. A critical problem is that associated with “stuck tools,” which results in expensive fishing jobs, lost tools and increased rig costs.
Stuck tool alleviation. Issues related to stuck pipe are as old as drilling itself. In “Development on Incongruous Pushing and Stuck Releasing Device of EFDT,” by Qin, X., Feng, Y., Song, W., Chu, X. and Wang, L. and appearing in Journal of China Offshore Oilfield Technology, Vol. 4, No. 1, April 2016, pp. 70-74, the authors analyze the causes of differential pressure sticking during openhole wireline logging. Their modular IPSRD releasing device, designed for EFDT formation tester applications, could be seamlessly assembled to the tool. “Stuck Release Arms” (SRA) are driven by hydraulic forces that free the dual probe tool from adhesive forces. In Chapters 4 and 5, we show how mudcake thicknesses can be accurately modeled and predicted – small values to reduce chances for tool loss are needed, while larger thicknesses are required to seal tester pads to the sandface – at the same time, providing excellent descriptions for supercharge pressure effects.
The authors importantly point out that while measuring pressure and sampling, even at a single point in the well, duration times may last several hours or even tens of hours. In particular, for higher mud densities, the possibility of differential sticking – and the likelihood of expensive fishing jobs – is high. In extreme cases, loss of the tool downhole and well abandonment are possible. Figure 1.18 explains the conceptual ideas behind IPSRD. The left diagram illustrates the differential sticking process, with the following nomenclature: 1-Wellbore fluid, 2-Backup, 3-EFDT, 4-Mudcake, 5-Probe, 6-Protector and 7-Formation. The right side outlines the tool architecture. Upper Stuck and Lower Stuck release modules USRM and LSRM are found at the top and bottom, with the Dual Probe Module (DPM) residing between the two. The “stuck release arms” (SRA) for each releasing module are designed in opposite directions for pushing separately. The paper describes several field applications and savings in logging costs.
Figure 1.18. IPSRD stuck tool release mechanism.
Field facilities. Finally, we offer some snapshots of COSL logging trucks and rigsite facilities from which formation testing jobs are run. The photographs are self-explanatory.
Figure 1.19. Rigsite facilities.
1.3 Recent Formation Testing Developments.
Conventional formation tester tools with single and dual probes are shown in Figures 1.8 and 1.9, noting that different testers may be outfitted with different pad designs depending on the application. For instance, small round nozzles may be used with firm matrix rock; in low permeability formations, larger nozzles may be preferable in order to prevent excessive pressure drawdowns that result in the undesired release of dissolved gas or increased mechanical demands. Larger slot nozzles are ideal when formations are lower in permeability
