Metrological evaluation of the mass balance of produced natural gas with gas lift from mature oil fields

Abstract

ABSTRACTGetting natural gas out of the ground introduces new supply chain challenges because the wells decline more rapidly than traditional ones. As time goes oil and gas fields become more mature, the internal energy of the reservoirs decreases and consequently the natural gas production does as well. A good strategy to overcome this challenge is to increase the participation of gas lift in this process. In Brazil, the measurement of produced natural gas is calculated by the difference between collected gas and gas lift. The more mature the oil field gets, smaller this difference is and more restricted the measurement capability is, reaching incoherently negative values, which can generate fines by the regulatory agency. This study presents a simple and new approach to evaluate metrologically the minimum difference between two input quantities in order to estimating the output quantity, here called measurement capability, applied to two Brazilian mature oil fields. The results show that for the mature oil field 1, there is the minimum difference of 370 m3/h and for the mature oil field 2, there is the minimum difference of 300 m3/h. High differences yield reliable results; however, minor differences from the measurement capability must not be considered. Historical values proposed are recommended.