Mandal, Dipak (Oil & Natural Gas Corporation Ltd) | Baruah, Nabajit (Oil & Natural Gas Corporation Ltd) | Jena, Smita Swarup (Oil & Natural Gas Corporation Ltd) | Nayak, Bichitra (Oil & Natural Gas Corporation Ltd)
Hydrocarbon gas injection into the reservoir is one of the most effective EOR processes. In case of a dipping and light oil reservoir, immiscible gas injection can give further impetus to the oil recovery. Since, average current gas saturation in the subject reservoir has become high due to depletion rendering water injection at this late stage is found to be ineffective, scope of gravity assisted immiscible gas injection as an alternative has been evaluated to assess its impact on reservoir pressure and ultimate recovery.
The present study pertains to a high permeable clastic light oil reservoir with reasonable dip, belonging to an old field of South Assam Shelf of India under production since 1990 with current recovery of 22% of STOIIP. The reservoir being undersaturated with no aquifer support, shows significant decline in reservoir pressure (260 ksc of initial pressure to current level of 50 ksc). Simulation study has been carried out on a fine scale geo-cellular model. Multiple realizations have been created considering combinations of oil producers and gas injection wells assigning varied rates to study the different development scenarios and impact on recovery improvement. The study indicates an incremental oil recovery of about 14% of STOIIP by immiscible gas injection.
Based on the study, immiscible gas injection has been initiated in the reservoir on pilot scale basis through two gas injectors with continuous monitoring. After gas injection during last one year, reservoir pressure increased about 25 ksc and consequently per well productivity also increased. Non-flowing well starts producing and currently sand is producing nearly 25% higher than earlier production before gas injection. Based on the encouraging result from pilot gas injection, decided to expand the process at field level and subsequently drilling of new oil producers after jacking up of reservoir.
The study has brought out that the gas injection into shallower portion of the reservoir yields better sweep efficiency to displace the oil to the deeper portion of the reservoir due to the gravity effects and hence, appropriate locales of the reservoir are targeted for additional input generation to augment the oil recovery.
Hazarika, Simanta (Oil & Natural Gas Corporation Ltd) | Rathod, P. Ramulu (Oil & Natural Gas Corporation Ltd) | Burla, Ravishankar (Oil & Natural Gas Corporation Ltd) | Das, Gour Chandra (Oil & Natural Gas Corporation Ltd) | Rao, Bkvrl (Oil & Natural Gas Corporation Ltd) | Deuri, Budhin (Oil & Natural Gas Corporation Ltd)
Subsea flow lines in deep water are typically exposed to high pressure and low temperature conditions which can create problems due to formation of gas hydrate. The gas hydrate formed can plug the flow lines causing not only loss of production, but may also create severe safety and environmental hazard. Moreover, dissociation of these plugs may take weeks or even months. Assessment of the hydrate formation potential during both steady is therefore an essential part of field development studies.
The paper presents a case study of a gas field located in KG basin of India which was brought on production in 2018. The objective of the study was to assist the on-site team on issues related to hydrate inhibition during ongoing initial start-up operation and assess the arrival time of rich MEG in the onshore plant in view of turn down flow conditions during commissioning.
The study also demonstrates how the transient simulations helped to monitor progress, identify and respond quickly to address the challenges during initial start-up operation of the deepwater gas field in Indian east coast. It emphasizes the need for accurate estimation of rich MEG arrival time and the minimum required gas flow rate from the subsea wells to ensure timely return of rich MEG to the onshore plant in order to avoid disruption in hydrate inhibition in the subsea system.
Singh, Rajesh Kumar (Schlumberger Asia Services Ltd) | Nangia, Viraj (Schlumberger) | Dunlap, James (Schlumberger) | Ghosh, Arnab (Schlumberger) | Roy, Dipanka Behari (Oil & Natural Gas Corp. Ltd.) | Klimentos, Theodore (Oil & Natural Gas Corp. Ltd.) | Bhattacharya, Shyamal (Oil & Natural Gas Corporation Ltd) | Sood, Pradeep Kumar | Agrawal, Ashwini Kumar
Hydrocarbon production from fractured basements holds great promise as an unconventional hydrocarbon source. These unconventional reservoirs are key in meeting the world's increasing hydrocarbon demand. However, basement characterization faces great technical challenges. Traditional formation evaluation methods, such as saturation estimation using resistivity-dependent equations, are often ill-suited to the basement environment because of complex mineralogy including conductive and heavy minerals. A workflow integrating the results from various advanced well log interpretations provides a robust foundation for successful tapping of hydrocarbon potential from fractured basements.
In the case study presented, a workflow is described in which the fractured basement underlying the sedimentary rocks of an offshore development field west of India was tested for the first time using the wireline-conveyed dual packer interval pressure transient testing (IPTT) technique. Pressure-volume-temperature quality oil samples were collected, gas/oil ratio was measured in real time, and formation pressure was recorded. The test was made possible by effective screening of potential test intervals using an enhanced workflow in which the newest generation of the nuclear magnetic resonance scanner was used for hydrocarbon saturation and permeability determination in conjunction with classical openhole logs and other advanced logs. Stoneley waveform analysis and borehole micro imager-derived results were useful in detailed fracture characterization and optimization of the dual packer position for a successful IPTT operation that proved oil production from fractured basement.