Close agreement was found between arithmetic mean pH values of limed samples and the pH values of composited samples. Agreement was consistently and considerably poorer when pH values were converted to H‐ion activities [(H+)] before averaging. Results are explained by the greater linearity between soil pH and base saturation (BS) in the acid range of mineral soils than between (H+) and BS. Linearity can be assessed by comparing average pH values with those of composited samples.
Many horizontal miscible gas floods experience relatively low vertical sweep efficiency due to gravity segregation of the injected solvent and reservoir liquids. This is true for the Prudhoe Bay Miscible Gas Project (PBMGP) in which the enriched-hydrocarbon miscible injectant (MI) is expected to sweep only approximately 30% of the reservoir volume in the project areas. The Prudhoe Bay reservoir has a relatively thick oil column, high inter-sand vertical permeability, high net-gross, and is generally developed on 80 acre (324 = 103 m2) well spacing.An infill drilling project was implemented in the Northwest Fault Block (NWFB) area of Prudhoe Bay (Fig. 1) to improve solvent sweep efficiency and increase EOR reserves. This project differs from many EOR infill drilling projects in that most of the additional recovery is attributable to EOR, with minimal improvement in waterflood recovery.The infill project is feasible because the reservoir is relatively thick, and sufficient EOR reserves are obtained from miscible displacement around new injectors. A significant increase in flood rate can also occur, resulting in production acceleration. Results of the project will guide analysis of infill drilling in other EOR areas at Prudhoe. The Prudhoe Bay Miscible Gas Project is the world's largest enriched-hydrocarbon miscible gas flood, and is located in northern Alaska, USA.
Introduction
This extended abstract describes the use of infill drilling to improve solvent sweep efficiency and EOR recovery in a gravity dominated WAG flood.
Much of the incremental oil recovery in the Prudhoe Bay Miscible Gas Project (PBMGP) is displaced from a relatively small volume of swept reservoir surrounding each WAG injector. Solvent override occurs due to high vertical permeability and the large density difference between solvent and reservoir fluids. Solvent rises to the top of the reservoir or underneath shales, forming cone-shaped swept intervals around WAG injectors (Figure 1).
Vertical sweep by solvent in gravity dominated WAG floods can be improved by increasing the viscous-to-gravity ratio1,2. A higher viscous-to-gravity ratio (HVGR) expands the solvent swept areas around the injection wells before gravity segregation occurs. However, little can be done in the PBMGP to reduce gravity forces, and water and solvent injection rates are currently near the maximum attainable.
Reduced well spacing remains the only viable method to increase viscous-to-gravity ratio. Most of the benefit from reduced well spacing is due to displacing oil from new WAG cones around the new injectors.
Information on the consolidation of soil media with depth-dependent elasticity, in accord with the one-dimensional theory, is presented. The information stems from a numerical evaluation of a Fourier-Bessel series solution for the relation between the degree of consolidation and the time factor. 1111 11 ß .
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