Development and Status of the Maljamar CO2 Pilot
Authors: Pittaway K.R. , Hoover J.W. , Deckert L.B. 
Published: December 2007

This paper describes the planning, testing, and decision-making steps that were taken in the development of the tertiary CO2, flood pilot in the Permian age carbonate rock formations of the Maljamar Cooperative Agreement (MCA) Unit. Injection and production history through 1983, a discussion of operating techniques and problems. and a summary of the logging results at the problems. and a summary of the logging results at the observation wells are given.

Introduction

The 5-acre [20 234-m2] Maljamar tertiary recovery pilot is in the Post-CO2 brine injection phase. CO2, in' was completed Dec. 11, 1983, Special features of the inverted five-spot pilot include dual (separate) completions in the Grayburg and San Andres zones and two fiberglass-cased logging observation wells for in-site monitoring of oil, brine, and CO2, movement, Estimates of operational costs and solutions to operational problems, as well as the process performance, are problems, as well as the process performance, are intermediate objectives of the pilot. The major objective is to provide a basis for commercial-scale CO2, flooding economics for the unit. Planning and testing included:(1)laboratory, slim tube tests to determine whether multicontact miscibility could be achieved under reservoir conditions,(2)a reservoir study to select the pilot location,(3)pressure transient tests to measure well and reservoir properties,(4)a pressure core to evaluate in-situ saturations,(5)geologic pressure core to evaluate in-situ saturations,(5)geologic studies to determine the depositional environment,(6)design of a tracer program to evaluate brine movement, and(7)a reservoir simulation to predict pilot flow performance.

These studies were conducted in several performance. These studies were conducted in several phases, each of which ted to decision points regarding phases, each of which ted to decision points regarding the future of the pilot. The pilot area was watered out and the tracer program was initiated before the CO2, injection phase.

The test is achieving its objectives by providing, data about field operations during CO2, flooding, as well as the process performance data needed to estimate commercial-scale CO2, flooding results in the field. Operating problems are being resolved and incremental oil production started in 1983.

General Information

The 8,040-acre [33×10(6)-m2 MCA Unit occupies about 20 % of the Maljamar field in western Lea County, NM. The Grayburo-San Andres pool was discovered in 1926, with the majority of the development occurring in the early 1940's. Wells produce from the Grayburg dolomitic sands and the San Andres dolomite at depths ranging from 3,600 to about 4, 100 ft 1100 to 1250 nil. Oil gravity is 35 to 37 deg API 10.85 to 0.84 g/cm ]. The pool originally was developed on 40-acre 11 6 ) × 10 3 pool originally was developed on 40-acre 11 6 ) × 10 3 m ] spacing with 20-acre [81 × 10 -m ] infill development occurring during 1971–73. In 1942, Grayburg-San Andres gas injection began in the MCA Unit. Lean produced gas was injected in 14 infill gas injection wells drilled on 160-acre [648 × 10 M ] spacing. This program was successful and improved the recovery of oil from the reservoir. In Nov. 1963, shortly after unitization, a water injection pilot began in the unit. Water first was injected into four wells, then after injection success was indicated, the program was expanded over the unit area in four major program was expanded over the unit area in four major stages during Aug. 1965 to Feb. 1969. The gas injection program was phased out as the various areas were put program was phased out as the various areas were put under flood. An infill development program was started in 1971 and gradually was expanded over the entire MCA Unit area. The infill development was to accelerate and improve the recovery of waterflood reserves. Additional recovery was attributed to reservoir heterogeneity and improved well completions. The field currently is developed with 80-acre (324×10 3 -m2) inverted nine-spot patterns, The pool is an anticline, which plunges in an easterly direction and has steep dips on the south side of the structure. Oil production is limited on the north by a porosity and permeability pinchout and on the south and porosity and permeability pinchout and on the south and east by an oil/water contact. Apparently, only very limited water influx occurred during primary depletion. There are one Grayburg (Sixth) and I-our San Andres (Upper Seventh, Lower Seventh, Upper Ninth, and Ninth Massive) pay zones under flood in the Maijamar field. Two other Grayburg sands (Fourth and Fifth) and one Lovington sand (Eighth) are productive in some parts of the unit. The total gross section from the top of parts of the unit. The total gross section from the top of the Sixth zone to the bottom of the Ninth Massive pay is generally 320 to 400 ft 198 to 122 ml. Reservoir and fluid characteristics are shown in Table 1. Expansion drive and solution gas drive were the primary drive mechanisms in the unit. The initial primary drive mechanisms in the unit. The initial reservoir pressure is not known; however, it is estimated to have been 1,300 to 1,350 psi 19 to 9.3 MPa]. The average reservoir pressure at the end of this phase and at the start of the waterflood pilot was 595 psi [4.1 MPa].

JPT

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