ELECTRONIC FLOW RATE-CONTROLLED PROBE PERMEAMETRY - THEORY, INSTRUMENTATION, ACCURACY, PRECISION, LIMITATIONS, AND APPLICATION

Probe permeameters have been widely used to characterize the spatial v ariations in permeability in core plugs, outcrops, rock slabs, and sla bbed cores. Constant pressure, rate, and volume boundary condition met hods are in nse. The portable, rapid, accurate, precise, inexpensive, and durable nature of our computer-interfaced electronic flow rate-con trolled probe permeameter makes it an ideal tool for making the large number of laboratory and field permeability measurements necessary for quantitative reservoir description and characterization. This equipme nt utilizes a precision mass-flow regulator to maintain constant flow rate, allowing steady-stare permeability to be calculated from a modif ied form of Darcy's law, while avoiding the need for inertial correcti ons. This approach requires no calibration to core-plug Hassler Cell s tandards and allows flexibility in adjusting seal-tip size or material . Hassler Cell permeability measurements were matched within 1 to 12% for homogeneous core plugs from 1 md to 45 darcys with a precision of typically 1 to 3%. The volume of investigation by probe-permeametry me thods has been addressed through analytical modelling and laboratory e xperimentation. According to our modelling efforts, streamlines and pr obed volume are independent of permeability and coincide in compressib le and incompressible steady-state flows. The effective radius of inve stigation was found to be about three to five times the internal tip r adius for injection. For negligible tip thicknesses, 80% of the inject ed fluid was found to exit the face of the prepared surface within a d istance of one additional tip radius, and 90% exited within five radii . In-situ polymerization experiments involving the injection of tracer compounds with styrene indicated hemispheroidal flow during steady-st ate probe-permeametry operation for homogeneous porous media. For a se al tip with internal diameter of 4 mm and outer diameter of 7 mm, the volume displaced by tagged styrene was 19 mm deep and 20 mm in diamete r when stable instrument readings were obtained. This confirms the Gog gin flow model, the use of the geometric factor, and the modified form of Darcy's law. These findings also impact surface-preparation proced ures and the maximum sampling density for independent data collection.