bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of Single Point Gas Lift System for a Deep Water Oil Field, India
Authors: Hazarika Simanta , Sinha Niladri , Bansal Rajeev , Jayaram Rajan 
Published: November 2015

Abstract
Single Point Gas Lift (SPGL) is preferred in subsea wells due to its certain advantages over conventional completion with unloading valves in meeting the aim for no intervention, pressure barrier requirements etc. Current paper presents a flow assurance study of an SPGL system in a deepwater field in India. The development strategy envisages clustered subsea wells with common flowlines connected to an FPSO about 12 km away.
Requirement of gas lift is envisaged from mid-life due to expected depletion in reservoir pressures and increase in water cut. Subsea gas lift in deepwater environment typically requires higher injection pressure to lift from desired injection depth. The gas lift, flowline and riser system is expected to operate over a wide range of conditions in terms of fluid composition, pressure and flow rates. Optimum design and operation of an SPGL system under such conditions is a challenge. Integrated dynamic modelling from down hole to host facility at the pre-FEED stage can provide valuable inputs for system design and operability.
The impact of various gas lift parameters like orifice size, setting depth, kick off pressure and operating injection pressure on the system has been studied. The field is having waxy crude with high pour point of 36°C with gelation propensity during long shut downs. The paper also brings out the operability windows during start up, turndown, shutdown, restart etc. and their impact on topside design. Transient modelling has been used to invetigate threats to system integrity due to high velocities of fluid through orifice, low temperature limits due to JT cooling, pressure surges into the production line resulting in large slugs arriving at FPSO. Slugging in riser may lead to process shut downs due to the pressure and rate variations resulting in loss of production. Design and optimization of the SPGL system is also aimed at increasing total production by avoiding process shut downs due to well instability and pipeline slugging.
Reliability Based Approach for Estimating The Fatigue Damage
Authors: Surendran Vasudevan , Rahayem Mohamed 
Published: November 2015

Abstract
Subsea diver-less connections in general are not subjected to fatigue load. By principle, they don't require a fatigue analysis, however, due to some uncertainties in field like slugging causes damage to these structures. Since these structures are not designed for fatigue, it is important to check its resistance and understand remaining strength when such phenomenon happens. The paper discusses about estimating the fatigue damage due to slugging phenomena which is a high frequency phenomena using combination of finite element and analytical solution. The loading action on the structure could be combination of axial force, transverse force and bending moment. The remaining fatigue life can then be estimated based on Miners rule. The paper also discusses about the probabilistic approach where variations in loading, material curve and Miners limit is considered to qualitatively understand safety of system for remaining service. For probabilistic analysis, reliability tools like Weibull analysis is used to assess the change in reliability of component and hence establish the relative damage in structure. Based on linear extrapolation of accumulated damage, using Miner rule based on DNV RP C203, the remaining life was estimated to be 9.69 years compared to 40 years of design life. However, the probabilistic approach is adopted to showcase that the slugging has lowered the reliability for fatigue failure of the critical component has dropped by less 20% for 9.69 years. The observation has led to increased confidence in operating the system in spite of accumulated damage. The approach presented in the paper can be used by the industry to understand the risk involved instead of taking decision based on remaining life computed using deterministic approach. The reliability based approach provides a qualitative assessment of extent of damage and hence assists in making a decision for risk based inspection and replacement.
Application of Dead Oil Viscosity for Water Shut-Off Job Designs in Reservoirs with Biodegradation: A Case Study of Bhagyam Field
Authors: Agrawal Nitesh , Mishra Lokranjan , Ghosh Priyam , Samal Saphalata , Priya Pachauri 
Published: November 2015

Abstract
This paper demonstrates a novel technique of tracking water entry zones, which has been used with a good success rate in Bhagyam field. Bhagyam field is located in the state of Rajasthan, India and is a part of the prolific Barmer Basin. Oil Production from Bhagyam field has shown steep decline as the water cut increased sharply. The reason for the increase in water cut can be largely attributed to adverse mobility ratio and limited volumetric pump capacities which limit drawdown. The excess water not only has reduced oil rates but also increased liquid volumes at the processing terminal. In order to control operating costs and increase oil production, it was of paramount importance for the operator to carry out water shut off jobs as a measure to reduce the undesirable water production.
This paper illustrates firstly a systematic approach on how the water entry zones are identified with the help of dead oil viscosity data and secondly describes a few case histories of water shut off jobs. Mechanical water shut off techniques were used to isolate bottom watered out sands temporarily. Retrievable bridge plugs were installed above the watered out zones during work-overs to increase drawdown on other sands and increase oil recovery. Using this methodology, four water shut off jobs were executed successfully in FY 2014–15 which led to significant reduction in water production and subsequent increase in oil production.
Reliability Analysis of Strength of Offshore Jackets in Indian Western Offshore
Authors: Singh Divjot , Panneerselvam N , Kumar Dinesh 
Published: November 2015

Abstract
Structural Reliability Analysis (SRA) is a method for estimating the reliability or probability of failure of a structure, a structural member, or a structural element. This analysis is in turn based on a physical model which represents both the load and resistance of the system. An offshore jacket is analysed for structural reliability and the major load on the jacket is found to take a parametric equation proportional to the maximum wave height impeding the platform. Reserve Strength Ratio (RSR) is used as a general term to describe the resistance of the system. Probability of failure of the structure is then calculated using FORM/SORM using MATLAB for different assumed values of RSR, and acceptance criteria of RSR for west coast of India is also discussed.
Case History: Largest Hydraulic Fracturing Jobs of India in KG Basin and Successful Production Test with Underbalanced Slim Hole Selective Completion in HPHT Environment
Authors: Pathak Shashank , Ranjan Vishal , Tiwari Shobhit , Ranjan Amit , Tripathi Archit , Nagar Ankesh , Singh Atul , Tibbles Raymond , Goyal Rajat 
Published: November 2015

Abstract
An appraisal well in the KG Onshore Block (a joint venture of Cairn India Ltd and ONGC) has provided key engineering and operational learning's. The objective of this well was to appraise two separate low permeability reservoirs (~ 0.1md) which are ~4300m deep and falls under HPHT conditions. Due to their low permeability; hydraulic fracturing was necessary to verify the production potential of these reservoirs. To cater this, the discovery well was re-designed and sidetracked so that it could handle the expected fracturing loads. Hydraulic fractures (~387,000 lbs of Proppant); biggest in terms of proppant placed in any single stage in India, were executed and then the well was completed with slim-hole selective completion in challenging underbalanced conditions to test these reservoirs selectively.
This paper primarily talks about the key constraints while planning and designing this well and then deals in detail on the learnings while executing this unique completion operation. Details on the fracturing design were already covered by Barasia et al. in SPE-171421-MS. The paper concludes with production results and the key reasons which led to ~7 fold increase with respect to previous appraisal well, as observed while production testing.
Innovative Completion Approach to Develop Unconsolidated Shallow and Thin Multi-Layered Gas Reservoir: A Case Study of North Tapti Field
Authors: Ahmad S. S. , Pradhan S. P. , Sarkar S. De , Sengupta S. , Bhattacharya V. K. 
Published: November 2015

Abstract
The North Tapti field is located in Arabian Sea WNW of Mumbai city. The bathymetry of the area is very shallow between 8-35 m depending on the tide condition and therefore poses adverse logistic conditions due to strong bottom currents. In North Tapti field shallow gas sands of Oligo-Miocene age occurring at depth of 550- 900 m are layered reservoir with several pays. Exploratory wells produced dry gas with sand. The lithology of the reservoir sand is mainly medium to fine grained and at places coarse sandstone with fair inter-granular porosity.
Initial development plan envisaged exploitation of gas through six development wells. All the six wells were envisaged as horizontal wells of about 300m drain hole with sand control completions through pre- drilled liner supported open hole gravel packs with a view to achieve higher gas productivity. The rig positioning activity in North Tapti area experienced great difficulties due to severe sand-scouring of seabed. Therefore, the first well had to be drilled as vertical well and completed with premium screen as a standalone screen completion with a view to make up lost time prior to impending monsoon. Studies based on the drilling data obtained from first development well revealed sub- surface surprises like reduction in pay thickness and occurrence of multi layered pays in Mahim and Daman formations at shallow depth. This posed considerable challenges in achieving desired high drift at shallow vertical depth of about 400m while maintaining high angle trajectory during drilling and subsequent completion programme. Hence, innovative drilling and completion approaches were adopted to tackle sub-subsurface complixities and to achieve maximum planned gas production.
In this backdrop of accomplishing the onerous task to produce sand free gas in all the six wells in platforms of North Tapti which were planned to be completed with suitable sand control methode using in-house expertise was a real challenge. The methodology adopted in two wells viz. A and B of 80° and 85° inclination were single frac pack and stacked completion of both. Stand alone in the lower barefoot section and a frac pack in the upper sands which was cased cemented and perforated. The wells of P1 platform are accessible with difficulty due to severity of water depth and short tide periods. Therefore wells were completed as stand-alone screen completions through Expandable Sand Screen (ESS) in 6″ drain hole section and 7″ liner sections.
This highly innovative drilling and completion approach facilitated exposure and completion of thin pay sands in multi-layered reservoirs in a deviated well. The result is stable and uninterrupted gas production for over a period of more than two and half years and continuing at a consistent rate of about 1.3 MMm3/d.
Workflow to Optimize Field Development Strategy and Maximize Recovery of a Shale Play
Authors: Sahoo Ajit K. , Biswal D. , Mukherjee A. , Srivastava M. 
Published: November 2015

Abstract
Due to the ultra-low permeability in shale reservoirs, hydraulic fracturing is necessary to provide secondary permeability to increase production in horizontal wells. Well spacing is a key factor in maximizing recovery of a shale reservoir. At the same it is important to understand the effective drainage area and the inherent reservoir quality to optimize the development strategy. In this paper, a workflow has been described to optimize field development strategy and maximize recovery of a shale play by integrating microseismic, DFN, tracer data and high frequency stratigraphic characterization.
In the first section, fracture geometry for the primary horizontal wells was estimated from microseismic data, tracer data and discrete fracture network model to establish the frac half-length, frac height and effective drainage area. From all these studies, it was observed that the hydraulic fractures of the primary wells are not able to drain the entire shale reservoir and a major portion of the reservoir remains un-drained. This analysis brought out an initial understanding about the requirement of staged lateral to exploit the un-drained reservoir section.
In the second section, various reservoir parameters were integrated with normalized well performance to capture the subsurface drivers that control the well productivity. Based on these critical drivers and gas in place, the above described un-drained reservoir portion was assessed to ensure its potential be a separate target.
In the last section, we have illustrated the importance of lateral placement through high frequency stratigraphic characterization. This analysis indicated that to maximize the well performance or recovery we need to place the lateral within the best part of the reservoir.
The illustrated workflow in this paper helps in deciding the optimum number of wells required to maximize field recovery. This study also helps in understanding the role of lateral placement in enhancing the well performance. This workflow can be applied to any shale plays which are in the initial stage of their development phase to understand if there is any scope of improvement in ongoing development strategy.
Channel Fracturing Technique Helps to Revitalize Brown Fields in Langepas Area
Authors: Valiullin Albert , Makienko Vladimir , Yudin Alexey , Overin Alexandr , Gromovenko Alexandr 
Published: November 2015

Abstract
Paper describes in details a trial campaign with channel fracturing technique and it's positive effect on operational reliability and wells productivity that helped to revitalize brown Urevskoe oil field.
Main challenges of the Jurassic formation are low permeability and high heterogeneity. Hydraulic fracturing is required for economic wells exploitation. Historically, hydraulic fracturing in oil fields close to the city of Langepas was developing towards aggressive designs with cleaner fractures, although increased risk of premature screenouts is encountered with such approach. To further improve efficiency and economics of stimulation treatments, a logical step in conductivity enhancement was made implementing channel fracturing technique. Channel fracturing allows for heterogeneous proppant placement leaving open channels inside proppant pack. Thus, conductivity of the system increases significantly. Channels also help to better clean out fracture from fluids and polymers increasing an effective fracture half-length, which is a goal in low-permeability formations. Another important advantage of the new technique is minimized risk of screenouts.
Campaign was made implementing the technique to re-stimulate wells in brown Urevskoe oil field in Langepas area. Open channels showed reliable production increase from old wells in depleted regions. Proppant flowback is a common problem in such conditions and was encountered in many offset wells, therefore channel fracturing was enhanced by rod-shaped proppant at the tail-in stage. Such combination allowed preventing proppant flowback issues and improved conductivity in near-wellbore zone.
Worldwide, this trial campaign is one of the pioneering re-stimulation projects implementing channel fracturing. Comprehensive analysis of performed operation, production comparative results and lessons learnt will make it possible to successfully extend the use of innovative technologies to many other brown fields that require stimulation.
Productivity Enhancement and Optimization in High Sour Gas Field by Selective Stimulation through Post Perforation Dynamic Underbalance Technique and Production Logging
Authors: Agrawal G. , Kumar A. , Verma V. , Mishra A. , Deori B. , Kaushik Y. D. , Gyani O. N. , Baishya R. C. , Shankar R. , Singh B. 
Published: November 2015

Abstract
XYZ, a marginal carbonate field in Western Offshore India was undertaken for development recently. During its exploration phase, around two decade ago, thick oil layer was discovered with high sour gas content (around 14000 ppm). The reservoir was delineated in small oil pool, where six wells were completed for production, including one water injector for pressure maintenance to support oil recovery. Production behavior of most of the wells had a unique response of rapid decline in short period of time with similar drastic loss in THP without any change in water cut. Production response of all these wells led the suspicion of near well bore skin development as the primary reason behind sharp decline in production.
Acid treatment as a quick fix solution in carbonates was ruled out because of possible communication with bottom aquifer; coil tubing had multiple operational challenges in such a high H2S environment. Hence, to overcome the challenges and perform root cause analysis, it was planned to carry out the best possible set of data acquisition with rigless operations and plan ahead for productivity improvement and design future intervention as well.
Production Logging, being an ideal diagnostic tool, was chosen to study the production profile and understand the reservoir and well behavior. Post analysis, a relatively new concept of selective stimulation with post perforation controlled dynamic underbalance technique was considered to be the best fit solution to address the skin and production decline problem in the field.
The technique proved to be very beneficial and provided substantial increase in the wells production. The skin debris obtained in the process were analyzed to identify the cause of skin development and production plunge. Based on the results, further interventions were carried out in the well, which again proved to be very efficacious and increased the field production significantly.
The paper has a detailed discussion on the root cause analysis and arriving to the appropriate solution for this kind of wells. It emphasizes on the importance of production logging prior to operation for better and successful planning and execution of the well intervention jobs leading to production gain. It also highlights the operational challenges in such hostile high H2S environment and the importance of planning and preparation to ensure safety of one and all.
Optimization of Hydraulic Fracturing Technology Application for Value Enhancement: A Case Study from Raageshwari Deep Gas Field
Authors: Gupta A. K. , Shankar P. , Saurav S. , Verma S. K. , Mund B. 
Published: November 2015

Abstract
The Raageshwari Deep Gas Field, Barmer Basin, India is a low permeability, moderate CGR gas condensate reservoir. It is a low net to gross system with gross reservoir thickness varying from 500-1000m. The pay zone consists of a poorly sorted sandstone interval on top of a stacked volcanic succession of thick lava flow cycles. The wells have been completed with multi-stage hydraulic fracture stimulations to allow production at economical rates.
The major challenge is to improve fracture placement to achieve wellbore connection with the entire net reservoir storage and flow capacity. Connecting each and every net reservoir packet would increase the number of fracture stages and in turn increase the cost significantly. Thus an optimization workflow was generated to increase the efficiency of hydraulic fracturing and reduce the cost of connecting the maximum net reservoir through hydraulic fractures.
An integrated approach including petrophysical and geomechanical analyses was used to identify the potential zones for hydraulic fracturing. Fracturing technologies like limited entry technique using cluster perforation were used to increase the net connected reservoir thickness while employing as few fracture stages as possible. Several post fracturing data acquisition programmes were conducted to estimate fracture parameters such as fracture height, half-length and conductivity to help evaluate the performance of each fracture stage. Single well analytical and numerical models were developed to estimate the impact of connecting maximum net reservoir thickness in terms of both initial production rate (IP) and the expected ultimate recovery (EUR) of the reservoir.
The limited entry fracturing technique with cluster perforation used in several wells was helpful in connecting the maximum net reservoir in the thick gross pay sections present. Based on a cost-benefit analysis, the number of fracture stages for each well was optimized with the goal of connecting the maximum net reservoir thickness to the wellbore. The fracture height achieved in each fracture stage was verified through micro-seismic, RST and temperature log measurements and pressure transient analyses. Once the height was ascertained, other parameters were obtained from post-fracturing pressure matches and pressure build up data. The estimated impact of connecting the maximum net reservoir storage and flow capacity as compared with the initial plan of 4-5 conventional single perforation hydraulic fractures is estimated to be production of ~5% GIIP in 15 years.
Mainstream Smoke Chemistry and in Vitro and In Vivo Toxicity of the Reference Cigarettes 3R4F and 2R4F
Authors: Roemer E , Schramke H , Weiler H , Buettner A , Kausche S , Weber S , Berges A , Stueber M , Muench M , Trelles-Sticken E , Pype J , Kohlgrueber K , Voelkel H , Wittke S 
Published: November 2015

Abstract
A new reference cigarette, the 3R4F, has been developed to replace the depleting supply of the 2R4F cigarette. The present study was designed to compare mainstream smoke chemistry and toxicity of the two reference cigarettes under the International Organization for Standardization (ISO) machine smoking conditions, and to further compare mainstream smoke chemistry and toxicological activity of the 3R4F cigarette by two different smoking regimens, i.e., the machine smoking conditions specified by ISO and the Health Canada intensive (HCI) smoking conditions.
The in vitro cytotoxicity and mutagenicity was determined in the neutral red uptake assay, the Salmonella reverse mutation assay, and the mouse lymphoma thymidine kinase assay. Additionally, a 90-day nose-only inhalation study in rats was conducted to assess the in vivo toxicity. The comparison of smoke chemistry between the two reference cigarettes found practically the same yields of total particulate matter (TPM), ‘tar’, nicotine, carbon monoxide, and most other smoke constituents. For both cigarettes, the in vitro cytotoxicity, mutagenicity, and in vivo toxicity showed the expected smoke-related effects compared to controls without smoke exposure. There were no meaningful differences between the 2R4F and 3R4F regarding these toxicological endpoints. The assessments for the 3R4F cigarette by smoking regimen found as a trivial effect, due to the higher amount of smoke generated per cigarette under HCI conditions, an increased yield of toxicant and higher toxicological activity per cigarette. However, per mg TPM, ‘tar’, or nicotine, the amounts of toxicants and the in vitro toxicity were generally lower under HCI conditions, but the in vivo activity was not different between the two machine smoking conditions. Overall, as the main result, the present study suggests equivalent smoke chemistry and in vitro and in vivo toxicity for the 2R4F and 3R4F reference cigarettes.