Abstract

In this paper, techniques have been developed to examine the effect of lamination on interpreting formation permeability in a hydrocarbon reservoir by numerically simulating the measured pumpout flow and pressure responses from wireline formation testing (WFT) measurements. With the field data obtained from a dual packer tool in the Deepwater Gulf of Mexico, a high-resolution near-wellbore numerical model has been developed and validated to simulate the fluid sampling process together with transient pressure. History matching has been performed with field data to assess the effective thickness and then interpret the permeability for each flow unit. Subsequently, eight cases have been generated under various configurations of the laminated layers. The pressure buildup derivatives obtained from both packers and observation probes are used as a diagnosis tool to examine the effect of lamination on WFT measurements. Mud-filtrate invasion affects the early-time behaviour of pressure transients because of the associated changes in fluid viscosity and compositions. It is found that low vertical permeability can behave as a vertical barrier for the flow in a WFT tool, indicating difference contrast in permeability between individual flow units. As for the field case, effective water horizontal permeabilities for Tests #1 and #2 are found to be 14.0 mD and 10.6 mD, respectively. A low vertical permeability results in a distortion in the derivatives, particularly during the transition between flow regimes. In a laminated reservoir, a radial flow regime will develop when both the radial length of lamination is greater than the vertical formation interval and complete circular shape of lamination is formed. It is recommended that any observation probe be positioned in or below the lamination layer to accurately define the vertical communication of lamination as well as its configuration. If the dual packers and observation probes are located in the same zone, their pressure responses exhibit the same flow regimes. If the dual packer and observation probes are located in different flow units, pressure changes in the observation probes can be developed when a partially sealing lamination exists.

You can access this article if you purchase or spend a download.