The Multiwell Experiment Core Program

Abstract

Member SPE-AIME Abstract The Multi-Well Experiment (MWX) is a research-oriented field laboratory and it is the major production technology activity of the Western Gas Sands production technology activity of the Western Gas Sands Project. A major activity is the core analysis Project. A major activity is the core analysis program. Over 3600 ft (1097 m) of core were taken program. Over 3600 ft (1097 m) of core were taken from two wells separated by only about 110 ft (34 m) at depth. All major categories of core analysis are reviewed and results through December 1982 are included. Those include routine core analysis, restored state reservoir parameter measurements, electrical measurements, mechanical rock property data, mineralogy, organic maturation and geochemistry. This paper also describes the laboratory work on core and formation invasion and the development of instruments that were used in the field processing of the core. INTRODUCTION - DESCRIPTION OF COPE PROGRAM The Multi-Well Experiment (MWX) is a research oriented field laboratory and it is the major production technology activity of the Western Gas production technology activity of the Western Gas Sands Project. The overall MWX objectives are to characterize lenticular gas sand reservoirs and to evaluate technology for their production. A major activity is the core analysis program. The magnitude of the MWX core analysis program has little precedent. About 2700 ft (823 m) of core were taken through the Mesaverde formation in the first well (MWX-1) and another 900 ft (274 m) were taken in the second well (MWX-2), as shown in Figure 1. About 700 ft (213 m) of this amount were oriented; this was divided nearly equally between the two wells. Core recovery exceeded 99% and the condition of the core was excellent. This was probably due in part to the use of oil-based mud and probably due in part to the use of oil-based mud and to the use of Stratapax coring hits. The two wells, located in the Rulison field of the Piceance Basin of Colorado, are separated by only about 110 ft (34 m) at depth. The features of the MWX core program included: (1) laboratory study of invasion of tight sandstone by an oil-based mud which is similar to that used in drilling the two wells; (2) development of a core gamma assembly for use in the field; (3) use of a laboratory apparatus for analyses of restored permeability and porosity measurements in a permeability and porosity measurements in a semiproduction mode; (4) development of special tools to provide more rapid determination of dip, strike, and bearing data on natural fractures and slickensides found in oriented core; (5) use of a special facility to perform field processing of core (e.g., photography and lithologic descriptions, core gamma logging, sealing of core, taking of plugs, and handling and shipping); (6) provisions for special core measurements at the well site (e.g., strain relaxation, desorption of coals, and collection of gas samples for chemical and isotope analysis); and (7) development of a core library with computerized inventory. Routine core analyses were performed at one foot (0.3 m) intervals river all the sands encountered, to help screen the core body for special core analyses. Over 1100 plugs were taken in the field from the MWX-1 core, and over 300 plugs were taken from MWX-2 core. Plugging was extended into the rock abutting each sand. Because oil-based mud was used, more meaningful water saturation data were obtained from core plugs. Perhaps more important than routine core analysis (and with little precedent) are the detailed special core analyses made. Dry Klinkenberg permeabilities at pressure and CEC measurements were made and thin sections were taken and analyzed every 1-3 ft (0.3-1 m) across the sand lenses and into the abutting "shales," or caprock. Relative permeability, capillary pressure, electrical measurements, and special mineralogy studies (e.g., SEM, x-ray) were performed on selected samples. Rock property measurements were also made across these sand-"shale" units. P. 437