ChevronTexaco has developed leading edge data acquisition and interpretation strategies to monitor steamfloods in Sumatra, Indonesia and San Joaquin Valley, California. This paper reviews ChevronTexaco's current steamflood surveillance techniques, and how learnings from San Joaquin Valley are adapted to operations in Sumatra.
Introduction
The Kern River field is one of the oldest and largest oilfields in California and has been produced for over 100 years. Oil gravity ranges from 10 to 15 API. Four major zones with multiple sands are present, each at varying stages of drainage.
The Duri field is the world's largest steamflood. It was discovered in 1941, first production was brought on line in 1956, and steamflood operations were initiated in 1983. Oil gravity ranges from 17 to 23 API, and oil is highly viscous when cool (> 100 cP @100 degF). Two primary and several secondary producing zones with multiple sands are present.
Time-lapse saturation and temperature profiles are developed from steam identification (pulsed neutron capture, cased hole neutron), Carbon/Oxygen, and temperature logs. Calibration of matrix Sigma in zones of 100% liquid saturation enables accurate steam/liquid saturation calculations using pulsed neutron capture logs. With the addition of a Carbon/Oxygen log measurement, a three-phase (steam/oil/water) saturation algorithm recently1 is applied to estimate remaining oil volume in the presence of steam chests. Cased hole log saturation calculations are validated against open hole saturations and core measurements.
The time-lapse profiles are then applied to find bypassed oil, estimate remaining reserves, identify depleted zones, and influence steaming strategy. As steam is the single largest operating expenditure in both Kern River and Duri fields, it is imperative to use it wisely.
Duri Field, Sumatra
The Duri field is the world's largest steamflood. It was discovered in 1941, first production was brought on line in 1956, and steamflood operations were initiated in 1983. Figure 1 shows the Duri Field location and Duri Area map.
Current production in Duri is 215,000 BOPD. Duri oil gravity ranges from 17 to 23 API, and oil is highly viscous when cool (> 100 cP @100 degF). Figure 2 shows a type log for the two primary producing intervals Pertama and Kedua. Secondary producing intervals are Rindu, Baji Jaga, and Dalam.
In Duri, there is on average 1 temperature observation (TO) well every 45 acres. Duri has 1500 injectors, with three times the steam injection volume of Kern River.
The current surveillance program in Duri consists of:Temperature profile in TO wells - 100% of TO wells surveyed once per yearTemperature profile in producing wells (Fiber Optic) - 5% of producers surveyed once per yearSteam IDentification (SID) / cased hole neutron - not used in DuriPulsed Neutron Capture (PNC) Sigma - 75% of TO wells surveyed once per yearKrypton/spinner profile in injectors - 50% of injectors surveyed once per yearCarbon/Oxygen (C/O) - 5% of TO wells surveyed once per year
Kern River Field, California
The Kern River field is one of the oldest and largest oilfields in California and has been produced for over 100 years. The location of the Kern River Field is shown in Figure 3.
