bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimum Technique Selection for Underbalanced Drilling in Iranian Oil Fields—A Review of Three Major Oil Fields
Authors: Hooshmandkoochi Ali , Zaferanieh Mehdi , Malekzadeh Amin 
Published: December 2007

Abstract
Underbalanced drilling technology (UBD) has enabled the commercial development of numerous oil and gas reservoirs worldwide. Underbalanced drilling was only possible through the integration of many developing technologies including directional control of the well trajectory, bottom hole circulating pressure and the safe handling of drilling fluids and cuttings. Technological advancements have permitted efficient recovery of wellbore liquids and gases to aid in the economic feasibility of employing underbalanced drilling technology. After a successful pilot project in Gachsaran field in southern Iran, National Iranian Oil Company (NIOC) has decided to develop this technology (UBD) in Iranian reservoirs. A study had been done to evaluate the feasibility of using UBD in the Iranian fields. This paper investigates the feasibility of drilling underbalanced in the Karanj, Parsi and Maroon reservoirs to reduce formation damage through invasion of drill cuttings into the formation and to increase the rate of penetration. Also in this paper, multi-phase fluid flow simulations which include drilling fluid, injected gas, formation fluids and cuttings, were carried out for different well geometry in these fields to obtain the optimum underbalanced technique by which underbalanced conditions can be obtained with the planned UBD equipment provided by NIOC to be utilized.
It is concluded that UBD technology is suited for all of the fields detailed in this paper. Having said this, Parsi and Maroon are ideal for underbalanced drilling as a minimal amount of adjustments to the overall drilling plan needs to be completed. For Karanj, underbalanced drilling is possible but may need additional UBD engineering and modifications in the overall UBD program in order to obtain UB conditions. UBD operations are feasible and a two-phase circulation system utilizing concentric casing nitrogen injection is recommended in the majority of the fields. In other fields where UBD conditions are more difficult to obtain, drill string injection is recommended as the most effective method for drilling the reservoir section of these wells underbalanced.
Fluid Customization and Equipment Optimization Enable Safe and Successful Underbalanced Drilling of High-H2S Horizontal Wells in Saudi Arabia
Authors: Hallman John H. , Cook Iain , Muqeem Muhammad A. , Jarrett Clark M. , Shammari Hamoud A. 
Published: December 2007

Abstract
Saudi Aramco planned to drill three horizontal wells underbalanced in the Uthmaniyah Field in Saudi Arabia but concern was raised because the large volume of fluid produced would also contain a high concentration of H2S. A detailed engineering study was conducted of the well parameters and it was recommended that a diesel-based fluid system be used initially for compatibility, cuttings carrying capacity and pressure control. Since the underbalanced operation was based on the flow drilling technique, the drilling fluid system was diluted and became a produced oil system as the underbalanced drilling operation progressed.
An important part of the design and treatment program was the minimization of H2S exposure for personnel on the rig site. A preliminary review of the operation revealed the areas of greatest concern; and the equipment layout was designed to ensure efficient separation and permit fluid treatment at surface. Laboratory studies recommended a proprietary oil-soluble H2S scavenger to remove residual H2S in the circulating fluid, and treatment points were selected for optimal performance.
All three wells were successfully drilled in an underbalanced condition. There were some minor H2S releases on the first well at several open points in the system, requiring a reassessment of the separation layout and design, particularly in the solids control equipment, and in the fluid treatment program. Once this was accomplished, the subsequent wells proceeded more smoothly. H2S levels in both the liquid and gas streams were monitored and showed very good removal efficiency despite the high production of both oil and gas from the wells.
This paper describes the design of the fluid system and separation equipment for the three wells. It will also highlight results from all three wells, showing the learning experience and optimization of the drilling operation from a fluid engineering and treatment point of view, as well as recommendations for future wells.
Coiled-Tubing Underbalanced Drilling Applications in the Lisburne Field, Alaska
Authors: Johnson Mark , Brand Patrick , French Sam , Sarber Greg , Hildreth Dave , Harris Bob , Rangel Pedro , Cassee Udo , Clark Jimmy 
Published: December 2007

Abstract
In 2005, BP Alaska began evaluating the application of Underbalance Drilling (UBD) Technology as a method for drilling multilateral wells in the Lisburne Field. The evaluation process was enacted as a response to three key challenges at Lisburne:
Slow Rate of Penetration (ROP) through the Wahoo’s hard carbonate formation, Frequent total losses of drilling fluid when drilling conventionally, Poor understanding of the orientation, frequency and impact of fractures on production.
The main objective of implementing underbalance technology in the Lisburne Field was productivity improvement. This was to be realized by improving ROP, thereby allowing for long laterals to be drilled, intersecting more fractures. Coiled tubing underbalanced drilling (CT-UBD) would also allow for drilling multi-lateral sidetracks from a single parent wellbore through the production tubing. In addition, it was felt that underbalanced drilling would eliminate losses to the formation, with a side benefit of potentially mitigating formation damage.
A two well, 5 lateral pilot project was approved. The 6th generation Alaska coiled tubing drilling rig, in continuous service since 2002, was adapted for use in an underbalance drilling mode. Due to the harsh North Slope winter climate and desire to minimize impacts to the environment, the UBD surface kit was designed to be small and to eliminate the need for flaring. This dictated that returned fluids be processed and sent to the production facility at or above pipeline pressure. A significant amount of front end loading was conducted to help ensure safe delivery of pilot objectives.
The pilot was completed during the summer of 2006 with excellent HSE performance. Although not without operational problems, the project demonstrated that underbalanced drilling could be used to increase rate of penetration and bit life. The pilot also demonstrated that underbalanced drilling could eliminate many of the hole problems associated with conventional drilling, making the drilling of long reach multilaterals feasible. The drilling rate more than doubled and a record Lisburne CTD horizontal length of 2,564 ft was achieved. The pilot also demonstrated the challenges and strengths of real time formation evaluation in identifying productivity features in the wells. Over 9,000 ft of lateral length was drilled and 14,000 barrels of oil were produced during the drilling operations. The cost of the project was 22% less than the cost per foot of overbalanced drilled wells in the same field. Additional underbalanced drilling is being contemplated for the future.
Near-Balance Drilling and Openhole/Liner Completion Proved to be Effective in Production of High-Pressure Low-Permeability Fractured Carbonate Reservoir
Authors: Wang Xi , Chen Peng , Xin Junhe , Wei Yuxiang , Zhu Aijun , Wang Xugang 
Published: December 2007

Abstract
It was difficult to drill and complete the wells in the Kenkiak Under-Saltdome oilfield in Kazakhstan due to complicated geological conditions. Among 42 wells which had been drilled by former operator 40 wells were abandoned; amid 40 abandoned wells 12 were engineering abandoned; only 2 wells were capable of production with 38 to 69 tons of oil per day. Because of low drilling rate of success, long cycle of drilling, and low production, the former operator regarded the field an unable to be developed one. Consequently the field had not been put into production since its discovery 30 years ago.
In order to increase the productivity, near balance drilling and open hole completion have been accepted for vertical wells in the beginning in high pressure low permeability fractured carbonate reservoir. The first trial met with success and initial day rate of production was as high as up to 480 tons of oil. Subsequently, near balance drilling and open hole completion have been adopted for other vertical and high-angle wells, average day rate of production exceeds 300 tons per well.
However, a few wells completed open hole encountered tubing blocked when put into production, which resulted in those wells off production. To prevent the wells from tubing blocked during putting into production, as well as to maintain high productivity, subsequent wells that are not suitable for open hole completion have been liner completed. Average day rate of production of those wells completed with liners also exceeds 300 tons per well.
Production of some wells completed open hole or liner exceeds 1000 tons per day per well. Open hole completion and liner completion have greatly increased productivity as compared to those wells completed perforation, turning it from an unable to be developed marginal field into one with annul capacity of 2 million tons of oil.
Evaluation of MPD Methods for Compensation of Surge-and-Swab Pressures in Floating Drilling Operations
Authors: Rasmussen Olve Sunde , Sangesland Sigbjørn 
Published: December 2007

Abstract
One of the main limitations in deep water drilling and drilling in depleted reservoirs is the low margin between the fracture and the pore pressure gradients. Drillstring tripping causes additional pressure variations in the borehole. The use of a Mobile Offshore Drilling Unit (MODU) in deep water results in even more severe surge and swab pressures, which are more difficult to control due to the MODU heave motion. Normally, no control of surge and swab pressure is possible during drillstring connections.
This paper presents the magnitude of surge and swab pressures that can occur in typical drilling operations, but will focus on Through Tubing Rotary Drilling (TTRD) operations. Most of the current methods for Managed Pressure Drilling (MPD) from MODUs do not have a functionality to compensate for both surge and swab pressures. A comparison and evaluation of selected MPD methods for compensation of surge and swab pressure are presented in the paper.
Changing the Look and Feel of Underbalanced Drilling
Authors: Ramalho John 
Published: December 2007

Abstract
Ever since Shell introduced underbalanced drilling (UBD) in the offshore environment in 1997, Shell has been looking at ways to reduce the footprint for the equipment required for underbalanced operations. Much of this work involved reducing the size of the separator (volume) and modularising the UBD kit by stacking and containerising. As UBD takes a foothold in low-cost operating areas, Shell has actively looked at ways to not only reduce the footprint but also the unit operating cost driven mainly by the need for experienced expatriate personnel to man the equipment. Recent introduction of new or improved tools and equipment combined with growing recognition that the primary value driver for the application underbalanced drilling is dynamic reservoir characterization, creates a window of opportunity to move this initiative forward.
This paper presents the conceptual framework to replace large, manpower intensive surface equipment with a combination of down-hole and surface tools and equipment having the same functionality but improved efficiency, which enable a reduced footprint.
It illustrates how the functionality of the 4-phase separator can be replaced by combining inline phase separation, a gas buster and down-hole multiphase metering. Furthermore it describes how massive surface snubbing systems are being replaced with down-hole isolation systems and proposes replacing current intrusive and high maintenance BHA equipment with low-cost rotary steerable systems, non-intrusive MWD systems and the development of non-return valves (NRVs) that are compatible with through bore solutions to optimise data gathering while drilling. The paper postulates that every piece of equipment is driven by a functional need, has an impact on efficiency and therefore cost and may offer opportunity for enabling add-ons if the underbalanced drilling process is viewed from a different perspective.
A Rigorous Reservoir-Wellbore Cross-Flow Equation for Predicting Liquid Inflow Rate during Underbalanced Horizontal Drilling
Authors: Guo Boyun , Shi Xiaodong 
Published: December 2007

Abstract
Underbalanced drilling (UBD) has been widely used as a means of reducing formation damage during drilling. The benefit of reduced formation damage results from the fact that the borehole pressure is intentionally maintained to be lower than formation pore pressure during drilling the pay zone.
UBD operations require additional surface equipment such as separators and reserve tanks to process and store the produced reservoir fluids. Selection of separators and reserve tanks for UBD involves using a method to predict reservoir fluid inflow rate and volume. Such a method is not available in the literature for UBD horizontal wells. This study filled the gap.
A rigorous reservoir-wellbore cross-flow equation was derived in this study for predicting liquid inflow rate during UBD horizontal drilling. A work procedure was developed to calculate fluid inflow rate and influx volume profiles. Application of the procedure is illustrated in solving an example problem. This paper presents drilling engineers a mathematical tool that can be used for sizing separators and reserve tanks during horizontal UBD planning.
An Investigation of PVT Effects on Geochemical Fingerprinting of Condensates From Gas Reservoirs
Authors: Al-Meshari Ali A. , Kokal Sunil L. , Jenden Peter D. , Halpern Henry I. 
Published: December 2007

Abstract
One of the tools used for the characterization of gas reservoirs is the geochemistry of gas condensates. The fingerprinting of liquid gas condensates by gas chromatography in particular, may provide information regarding reservoir compartmentalization, which can be a major uncertainty at the early field appraisal stage. An important concern is the capture of suitable liquid samples. When the flowing bottom-hole pressure falls below the dew point pressure, for example, condensate will drop out near the well bore and the captured sample may not be representative of the formation fluid.
We conducted three sets of tests simulating the effect(s) of gas-liquid phase fractionation on fingerprinting analyses: (1) at different pressures (all below the dew point) at reservoir temperature in order to simulate dropout of liquids in the near well bore area; (2) to investigate the effect of variations in separator temperature and pressure; (3) to evaluate fingerprint variations during a field deliverability test from a well that was previously shut in.
Geochemical fingerprints obtained on our laboratory fractionated samples show that condensates obtained from gas wells with flowing bottom-hole pressures below dew point may not be suitable for compartmentalization studies. Differences in separator pressure and temperature affect the fingerprints of gas condensates but the effects are small and unlikely to alter conclusions regarding potential fluid flow barriers. We suggest a number of best practices for the collection and analysis of gas condensates for fingerprinting studies.
Geomechanical Applications for Near-Balance and Dynamic Underbalance Perforating Technique in Overpressured Gas Zones in Burgos Basin
Authors: Campos Humberto , Martinez Sergio , Pizarro Hugo , Kessler Calvin , Torne Juan 
Published: December 2007

Abstract
Electric, acoustic, and nuclear logs, as well as rock properties information from cores and downhole tests, such as leakoff, minifrac, hydraulic fracturing, and pressure buildup, are normally available in the gas fields in Northern Mexico. The existing information was used to fully determine rock properties and to select the optimum perforating technique to minimize formation damage and to help produce gas from this type of reservoir.
The critical drawdown and formation compressibility were evaluated based on the integration of rock mechanical properties from dipole sonic and from density logs with core analysis information determining proper dynamic-to-static calibration parameters.
The process to design the perforating technique to maintain a balance between hole diameter for future hydraulic fracturing and maximum penetration to reduce the skin damage in this type of reservoir is presented in the paper. The results from different wells, as well as the advantages and disadvantages of the technique, are compared.
Well Integrity Assurance: A Successful Method for External Corrosion and Damage Detection on Outer and Middle Concentric Strings of Casing
Authors: Loveland M. J. , Burton Joey 
Published: December 2007

Abstract
As well integrity is of utmost importance for personnel safety and environmental interests there is an ever increasing need for tools and systems that verify and confirm the status of wells with suspect integrity. Recent near-surface, outer casing failures caused by external corrosion on relatively new wells in the Kuparuk Field of Alaska prompted research for a non-invasive predictive method to foresee failure and aid repair prioritization. There are a variety of tools and methods available to locate leak points and corrosion inside of tubulars, but very little literature exists concerning external corrosion and damage detection on outer and middle concentric strings of casing. The following method is a valuable qualitative approach used to determine existence and severity of shallow external surface casing corrosion before leaks occur.
The technique uses a logging tool that analyzes the variations of metal thickness within three concentric sets of down-hole tubulars and identifies areas where metal loss exists. The metal loss combined with assumed or known internal tubing condition reveals the wells with the highest risk for shallow surface casing leaks. When a high risk area is discovered proactive excavation repair plans can be made before any safety or environmental problems occur. This paper summarizes the tool, technical approach and assumptions, limiting factors, and the remarkable comparison between the metal thickness logs and the actual external surface casing corrosion observed on 12 wells after excavating each up to 27 ft in the Greater Kuparuk Area. Future plans and strategy using the technique are also discussed in the paper.
A Mentor/Mentee Training Program: A Success Story
Authors: Al-Meshari Ali , Kokal Sunil 
Published: December 2007

Abstract
To sustain the energy needs of the world you need people – more specifically specialists – who will carry the ball and push the envelope of technology further. How do you develop young engineers and scientists to become productive specialists? This paper presents a success story of a "Specialist Development Program (SDP)," implemented at Saudi Aramco that can be the basis for others to follow. It highlights the "mentor-mentee" relationship, the bedrock for the hugely successful program1.
The program was established several years ago with the objectives of providing qualified Saudi engineers and scientists with an opportunity to become engineering/scientific specialists, and providing the company with high-level technical expertise in the specialties for which the company has a critical need. The program has a structured, streamlined, and phased career path for identified specialties, attracting qualified candidates and matching them with the most appropriate mentors. This strategy ensures candidates obtain the required experience, further education and exposure for their chosen specialty. The program serves as a roadmap for optimizing the professional growth and advancement of candidates. It is also sufficiently flexible to respond to candidates’ training and work requirements, while enabling them to achieve higher levels of competence and productivity. This paper highlights the salient features of the unique and successful development program, focusing on the mentor-mentee relationship. It describes the program, the current specialties, mentee and mentor requirements, roles and responsibilities, criteria for graduation, and tracking.
Screenless Frac-Pack Completions—Case Studies from Jidong Fields, China
Authors: Jun Chang Xue , Bao Chen Ren , Lubis Wirdansyah , Hui Deng , Nguyen Philip 
Published: December 2007

Abstract
Productivity of the well often declines rapidly as a result of fracture conductivity loss suffered by proppant flowback and high water cut. In wells with conventional frac-pack completions, sand control screens have often shown signs of damage caused by fines plugging, erosion, and/or corrosion. To combat the proppant and formation sand flowback problems, field trials of an on-the-fly coating curable-resin system were performed to determine whether this resin system is a viable option that can provide an effective means to establish screenless frac-pack completions in this field. This paper presents the results of these field trials involving the screenless frac-pack completions using an on-the-fly curable resin coating system. Detailed descriptions of the completion procedures, the challenges, and lessons learned during the course of these frac-pack treatments are presented.
This study has determined that an optimum concentration of resin coating on the proppant is necessary to maximize the bonding between proppant grains and the consolidation strength of the coated proppant pack while minimizing any reduction of its conductivity. Field results indicate that this on-the-fly resin coating treatment effectively stopped the proppant and formation sand from producing back while maintaining the production rates as designed and has drastically decreased the number of workovers compared to the same wells left untreated. The technique provides a very attractive alternative to conventional frac-pack completions in wells with marginal reserves, eliminating the need for sand-control screens and providing access to other intervals when needed without wellbore restrictions.