This paper describes the measurement of crude oil volume in an oil/water mixture that discharges from an oilfield. Measurement is carried out using a turbine meter, a densitometer and a flow computer. The system is capable of determining the volume of crude oil in a flowing stream of a crude oil/water mixture within 2% of the total liquid volume.
Baram Delta is located off the coast of Sarawak, East Malaysia. The producing fields within the Basram Delta comprise the Betty, Bokor, Siwa, Tukau, Baronia, Bakau, Baram, Fairley-Baram and West Lutong fields. Betty, Bokor, Siwa and Tukau are currently being operated by Sarawak Shell Bhd (SSB) under a Production Sharing Contract (PSC), signed between the Malaysian National Oil Company (PETRONAS) and SSB in 1976. The remaining fields are also being operated by SSB, but for and on behalf of a Joint Venture between SSB and Petronas Carigali Sdn Bhd (PCSB) under a PSC signed in 1985 between PETRONAS and the Joint Venture parties. The said fields, Baronia, Bakau, Baram, Fairley-Basram and West Lutong, were relinquished by SSB under the terms of the PSC signed in 1976.
The existing liquid measurement and reallocation procedures are in general sufficiently accurate to meet the requirements for fields and reservoir management. However, the process of reallocation of crude oil between the fields operated under the terms of the 1976 PSC and the fields operated under the 1985 PSC, leaves a non-quantifiable uncertainty which could introduce errors larger than 2% of the gross volume. This was the maximum error specified by a Task Force comprising PETRONAS, SSB and PCSB and agreed by all parties in early 1986. Hence, a new measurement system was proposed. As its use for the application intended is without precedent, a laboratory simulation and a pilot test of the system were carried out. This paper deals with the tests carried out to prove the reliability and suitability of this system in oilfield conditions.
The theory of calculating the net oil volume and the mixture volume flowrate at standard conditions is summarized in the flowchart below.
Volume flowrate Computation of % of mixture at mass of oil in line conditions oil/water mixture Q(m1) Density of mixture at line conditions> D(m1) Mass flowrate of > mixture M(m) Mass flowrate of Density of oil M(o) mixture at standard > conditions D(ms) Density of oil < at standard Volume flowrate conditions D(os) of mixture at standard conditions Q(ms) Volume flowrate of oil at standard conditions Q(os) Totaliser