Oil India Limited (Oil India) is considering adapting new technologies to ensure that oil and gas strategic resources are optimally explored, developed, and produced during the life cycle of their fields. Underbalanced Drilling (UBD) technology, which can achieve these objectives effectively when applied in conjunction with horizontal drilling techniques, is being considered among various options.Accordingly, Oil India decided to pioneer the introduction of this new technology in their onshore oilfields by employing a systematic scientific approach to screen the Makum-North Hapjan Oilfield for UBD candidacy. The screening process involves detailed evaluation of reservoir, production, drilling, geology, geophysics, and operational data with risk analysis incorporated into a rigorous expert system aimed at maximizing the value of any UBD operation. The screening process was performed in two phases: a low resolution screening and an in-depth high-resolution analysis.Phase I objectives were to evaluate and rank Oil India's reservoirs for UBD in comparison to conventional (overbalanced) drilling techniques, compare candidate reservoirs against global database of UBD analogs and select a candidate for phase II detailed reservoir damage analysis and productivity forecast. Phase II objectives were to identify the formation damage mechanisms that are expected to occur in each of the three reservoirs and determine productivity and economic improvement of underbalanced compared to overbalanced drilling. This paper describes the expert system methodology used and provides a discussion of the results obtained. Phase II study findings provided Oil India with confirmation that UBD could provide improvement compared to conventional drilling and completion technologies. The scope of the study also included a complete engineering evaluation for drilling and completion of a new horizontal well -underbalanced, including the use of a downhole isolation valve. The UBD Screening ProcessThis paper investigates the reservoir suitability of underbalanced drilling using an Expert System screening process that was developed in conjunction with leading industry consultants to increase success in candidate selection and to evaluate the benefits of underbalanced drilling over traditional drilling and completion technology in terms of reservoir performance.The screening process began by taking basic information for the candidate reservoirs and processing the information through the expert system software. This software rates the candidacy of the reservoir to help determine the likelihood of achieving success with underbalanced compared to overbalanced drilling and completion techniques. All data input was reviewed for completeness and consistency.Based on the screening process findings and Oil India feedback one reservoir was selected for further evaluation (Phase II). This in-depth phase integrates geological, reservoir, production, drilling and completion data to calculate a near wellbore damage. The calculated drilling induced damaged is the...

Gas lift plays a major role in the oil production operations of mature depleted fields of various E&P companies worldwide. Likewise, in Oil India Limited, India about 48% of producing wells of Upper Assam Basin are on gas-lift assistance. In this project, we have started and completed a gas-lift optimization campaign in Hapjan field, one of the brown fields of Oil India Limited. This project includes complete problem troubleshooting and optimization study of all the 23 gas lifted wells of the mature field. All gas lifted wells of the Hapjan field are intermittent lift by design and are operating with surface intermitters. As such, all available diagnostic tools developed and available for intermittent gas-lift well optimization are aggressively used during this campaign. The used tools are as mentioned below:Two-pen pressure recordings.Gas volume measurements.Acoustic surveys.Downhole pressure/temperature and long cycle surveys.Revamping of compressor station. In the present optimization campaign, entire candidate wells of Hapjan field were included and the endeavor has resulted in crude oil production gain of 76 m3/day, which is 11.8% growth of the total production of the field. In addition, based on the results of the comprehensive study of vertical regime of the wells, 3 wells have been taken up for recompletion. Moreover, the gas volume in the injection gas network have been increased from 280000 Scmd to 340000 Scmd with the commissioning of a new compressor, and by revamping of the all other compressor units of the station. This has further supported to reallocate the required gas quantity in each individual well as per the design volume. The technical experience and knowledge gathered from this gas lift optimization campaign certainly confirms that optimization of gas lifted wells is a vital tool to boost up production in mature depleted fields in Oil India Limited as well as in other exploration and production (E&P) operators worldwide.

High angle S-shaped and high displacement L-shaped well profiles are preferred now-a-days in Balimara field located in the northeast region of India. Main targets are the deep Clastic reservoirs of Oligocene age. Major events reported are while drilling against dipping formations with differential stuck pipe situations with variety of drilling complications in the unstable formations owing to shales in Tipam sandstone and thin sections of coal and shale alteration in oil bearing Barail sandstone formation. The substantial risk of wellbore instability in accessing the reservoirs with lateral variation in pore pressure threatened the commercial success of the project. This paper elaborates how geomechanical information along with BHA design and chemicals was integrated into the decision-making process during well design and drilling operations to avoid wellbore instability issues. Wellbore stability analysis through Mechanical Earth Model was conducted using estimated state of stress and mechanical properties of the overburden and reservoirs. The model incorporated data from several sources including geophysical logs, leak-off tests, advanced sonic far field profile and drilling records collected from the earlier wells. Examination of the deviated well bore profiles suggested occurrence of ledges due to lower mud weight and improper drilling parameters while drilling alternate layers of sand, shale and coal in Barail formation. Horizontal stress contrast increases in Barail formation supporting the need of higher mud weight with increased well deviation towards specific azimuth. The integrated geomechanical analysis provided key information: The 9 5/8" casing shoe should be set at shale layer of Tipam Bottom to isolate upper differential sticking prone sandstone layers with Barail Argillaceous sequence. This will help to drill 12.25-inch hole with 9.6 ppg-9.8 ppg only. Shale layers at Tipam bottom require 10.0-10.5 ppg, while Barail shale requires 10.5 ppg-11.0 ppg for vertical well. When the well deviation increases up to 30deg, mud weight requirement rises to 11.2 ppg-11.8 ppg. Based on analysis, the mud weight at the start of 8.5inch section was raised sufficiently to 10.5 ppg to avoid the hole collapse experienced in the earlier lower angle wells. Later, continuous review of torque and drag along with cutting analysis helped to raise mud weight up to 11.0 ppg till well TD. As a result, lower UCS shale and coal layers are drilled with minimal shear failure and improved hole condition. However, changes to the mud system were needed to limit fluid loss and avoid differential sticking across the sandstone. For deviated section, rotary BHA has been used to improve hole trajectory vs. planned with lesser ledges. Downhole hydraulics has been maintained with proper flow rate and rpm to main hole cleaning. The new well engineered with the integrated geomechanics information has been drilled from surface to extended TD while saving 15 rig days.