Prabumulih Field was located in South Sumatra, Indonesia. It has been developed as an oil field since 1920n (It was categorized as a mature field). At the end of 2019, the amount of oil well production was 149 wells (93% of the producing wells installed artificial lifting). As a consequence, to maintain production, artificial lifting surveillance activities must be a major concern and be managed properly. However, there are some challenges for surveillance, for instance, the location of well spread over a large area, the condition of the access road, and limited human resources. Surveillance activity itself carried out manually required both much time and many human resources, however, acquired data was only once in a week for one well. That condition always emerged undesired occurrence because engineers who were in the headquarter did not obtain notification when producing wells were in trouble or suddenly off producing. In addition, there was a delay in time for evaluation and intervention, which resulted in decreased oil production. Nowadays, application, in order to accelerate the data retrieval process, was much needed, especially real-time acquisition and it could be monitored in several kinds of devices. This paper will be presented about the benefit of real-time monitoring application in mature field, especially for artificial lifting well (ESP and Rod Pump). It has been installed since December 2019. There were several benefits obtained after installing this technology, those were related to surveillance and optimization. For instance, reducing time and human resources needed to obtained pump parameter data, engineers who are in the headquarter could observe everyday using both laptop/personal computer and smartphone, engineers obtained notification immediately when there were wells in a trouble, decision making for optimization and or intervention was faster, increase pump run life, and reducing well service program. Besides, there was another benefit that related to cost reduction, for instance saving rig costs for well service of 350,578 USD in a year because the amount of well service decreased from 49 times to 36 times, and obtained additional gross revenue of 547,945 USD for one year (cost for real-time monitoring for a year is 116,438 USD) because production deferment reduced from 19,577 STB to 5,105 STB. Based on those data, real-time monitoring could increase the economic condition of the mature field, so it was worth applying in a mature field.
Freshwater environment and high clay content are quite common in Indonesia. This introduces certain challenge in performing hydrocarbon identification and evaluation especially in already cased wells. In old producer wells, possible conditions such as fluid channeling behind casing and trapped hydrocarbon in annulus add more complexity in performing behind casing analysis to understand current reservoir condition. In order to increase the success in finding remaining hydrocarbon potential, PERTAMINA has deployed pulsed neutron logs (PNL) to accurately pinpoint the targeted interval for perforation. Since 2017, the PNL campaign has covered approximately 160 wells in PERTAMINA's development fields across Indonesia up until now. PNL service offers nuclear-based statistical measurement such as sigma, thermal neutron decay porosity (TPHI), and carbon-oxygen yield that allows simultaneous oil and gas saturation evaluation without any dependence on water salinity and other electrical properties of the formation and fluid. It also allows computation of elemental dry weight from elemental spectroscopy data which can be utilized to determine lithology to complement the standard open-hole logs dataset. The more advanced PNL tool raises the bar even further by offering new measurement of fast neutron capture cross section (FNXS) log which is useful to identify gas even in tight rock formation. The latest generation also features self-compensation algorithm resulting in more robust TPHI and sigma log under complex circumstances such as multi-casing/tubing. This paper showcases several prominent success stories of oil and gas findings identified from PNL interpretation in development wells. There are also several examples of elemental spectroscopy data utilization from PNL to prevent non-economical perforation by means of providing accurate lithology and porosity analysis as compared to previous result built from old and/or incomplete open-hole logs dataset. This PNL campaign has also given valuable insights of borehole and reservoir condition which might have been overlooked such as hydrocarbon in annulus, low pressure gas zone identification and batman's ear boundary effect. Low pressure gas zone may be qualitatively identified whenever TPHI from PNL is noticeably lower than neutron porosity measurement from the open-hole log. Batman's ear effect is usually observed when a body of sand is sandwiched between carbonaceous shales or coal layers resulting successive oil-water-oil saturation profile in one homogenous body of sand, shown as oil peaks at the bed boundaries similar with the appearance of batman's ear. As the sand gets thinner, these two oil peaks might merge into one solid body of high oil saturation which might not depict the true oil potential of the sand.
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