bluuebunny/crossref_metadata_2025 huggingface dataset:
Oil Invasion in Gas Zone and Sweep Efficiency Due to Stratigraphic Barrier in an Active Waterdrive System, Hollin Formation, Ecuador
Authors: Ucan Sezai , Olmos Sebastian , Rios Sergio , Marin Horacio
Published: December 2007

The main objective of this study was to describe the nature, distribution, and physical characteristics of the reservoir, by integrating geophysical, geological, petrophysical, and production data in a three dimensional geological and simulation model that represents the behavior of the Hollin reservoir in Bermejo field. The Hollin reservoir required significantly higher effort due to the strong aquifer, the complex relationship between heterogeneity influences, the movement of the water from the aquifer into the reservoir, water and gas conning, stagnation of unproduced oil zones, and migration of oil towards gas zones.

When production data was analyzed, it was determined that even thin shales (on the order of 2-5 ft. or greater) played a role in enhancing reservoir production by delaying water and gas conning and water influx in the Hollin fluvial sandstone. Mapping the shale barriers was as important as mapping the sand bodies. It was decided to correlate the shales interpreted from well log data and introduce shale tops and bases in the geological model. Therefore, in the geological and simulation models shales have been modeled explicitly, down to a five foot resolution.

A Stratigraphic geocellular model was constructed to describe the 3D petrophysical properties, calculate hydrocarbons in place and to prepare reservoir simulation grids. Geological models incorporating shales were modeled. If shale was locally absent, the "shale zone" was assigned the appropriate reservoir properties determined from well and/or seismically derived attributes. J-Function analysis was implemented successfully in assigning oil saturation. Calculated oil saturation profiles at initial and current times were compared with initial well log oil saturations.

History matching and initialization were conducted to validate geological, petrophysical, PVT, and reservoir models. Flooded and non-flooded regions of reservoir, current WOC and GOC were identified. Areal extent of localized thin shale lenses were modified during history, matching active water breakthrough well by well. The amount of oil invasion in the original gas zone, stagnated oil, and gas contraction volumes were calculated in the most productive marker, Naranja. Current GOC has moved from the original GOC position. Actually, the amount of oil invasion was not significant when it was compared to the volume of stagnated oil.

When geological and simulation models are built and data gathered according reservoir specific problems, successful history matching and predictions can be obtained.
Look at the Behavior of the Reservoir, Well, and Facilities as an Integrated System
Authors: Cetkovic Ivan
Published: December 2007

A tool that enables full field economic optimization, driven by gas and oil prices and costs of equipment operation such as compressor fuel gas, water disposal or electrical power generation has become a critical feature. An integrated model helps the production engineer to evaluate and design surface equipment where the behavior of the reservoir and wells are been considered at the same time. These mean that any change on pressure, volume or temperature on the surface conditions will affect the wells and reservoir behaviors and vice versa. If we project this to all the phases of the field life, from planning through development and operations, the need of an Integrated Model becomes more critical.

Common questions from reservoir engineers of what the impact would be of increasing choke diameters, changing artificial lift methods, decreasing separators pressures or installing compression could be answered with an integrated subsurface-surface model. On the same way, questions from operational engineers of what the impact would be of drilling new wells, stimulating the reservoir or implementing a secondary recovery could be answered with a model that looks at the behavior of the reservoir, well and facilities as an integrated system.
Case Study: Mixing Proppant Sizes To Control Pressure-Dependent Leakoff
Authors: Cote A. J. , Crawford K. A. , Nguyen T. H.
Published: December 2007

One of the main factors affecting fracture treatment completion in the Cardium formation in North West Central Alberta is PDL. PDL is determined from minifrac analysis completed prior to the main treatment. PDL can be treated and controlled with a combination of increased fluid rates, additional 50/140 proppant (100 mesh) in the pad and increased gel loadings. Yet in certain areas even these precautions will not achieve successful placement of job design or effective fracture properties.

Common practice is to design for 80 to 100 Tonnes of ceramic proppant into each of these reservoirs, with an additional 5 to 7 Tonnes of 50/140 proppant in the pad to control PDL. In most areas this works effectively for controlling the competing fracture leak-off during the treatment. In the Northwestern Alberta Cardium area this approach has not been as successful and has caused concern about total proppant placement.

An alternative approach for controlling fluid leak-off during the treatment has been to mix in a small amount (usually 5% by weight) of 50/140 proppant with the ceramic proppant in the early stages of the treatments to control the fluid leak-off in these areas. Treatment design engineers recognize the fracture conductivity issues caused by mixing different mesh sizes. However, utilizing this approach has resulted in full job completion and this paper will discuss the specific treatment designs required to drastically limit fracture treatment screen-outs.
Aluminum-Based HPWBM Successfully Replaces Oil-Based Mud to Drill Exploratory Well in the Magellan Strait, Argentina
Authors: Ramirez Mario A. , Benaissa Saddok , Ragnes Gerald , Almaraz Angel
Published: December 2007

Traditionally, Oil Base Mud (OBM) has been used by a major operator to drill horizontal wells in the Magellan Strait, Argentina. The operator was faced with additional challenges when drilling an exploratory well due to environmental concerns in a highly sensitive area and evaluation problems related to the use of OBM. Significant advances in water based drilling fluid design in the recent years have allowed water-based drilling fluid performance to approach that of OBM. This presented the operator and drilling fluids supplier with the opportunity of evaluating the application of water base drilling fluid on this well. The planning stage included laboratory testing, review of historical data and an evaluation of experience with similar shales in the area. A high performance water base drilling fluid containing both clay and shale stabilizers, an ROP enhancer and sealing agents was selected to drill the well.

This paper presents the laboratory and field data generated during this project. The well was drilled through notoriously troublesome shales to total depth without the wellbore stability problems associated with more conventional water based muds. Gas kicks were controlled with no fluid solubility problems and the fluid exhibited excellent properties even when pressure parameters escalated higher than planned, requiring a higher mud density and high degree of temperature stability. The operator's expectations were met in this very difficult well including minimization of bit balling, near gauge hole and improved ROP in conjunction with optimum hydraulics.

The evidence gathered on this project shows that a properly designed water base mud is a viable alternative to OBM in areas where environmental restrictions and formation evaluation problems are a concern.
Sustainable Deployment of Geomechanics Technology to Reducing Well Construction Costs
Authors: Mody Fersheed K. , Tare Uday , Wang Gary
Published: December 2007

Over the past two decades the Geomechanics community has made substantial contributions to the petroleum industry in reducing well construction costs, maximizing production and increasing the life of the well. Borehole (in)stability, lost circulation, stuck pipe, sand production, casing collapse, well failures, and sub-salt related issues are real and can happen unannounced when we are not vigilant and proactive in avoiding them. Prevention is always better than the cure and we all should strive towards preventing these geomechanics related non-productive time (NPT) crises. This paper will be focused on the sustainable technology deployment to bridge the gap and realize the rewards associated with it.

The technical issues that are addressed in this paper are:

Deployment of technical resources to solve borehole (in)stability-related problems, which cost the industry billions of dollars. Using the right resources (i.e., man power, budget, data, etc.) to bridge the gap. However, in order to bridge the gap, geomechanics technologists should be more proactive in capturing the value of technology successes and continuously educating management about the value it creates.

In summary, the industry cannot afford to lose billions of dollars on geomechanics-related NPT and associated lost revenue. Hence, it is critical to manage the available geomechanics resources in the optimum manner. It is important to identify challenging wells and get the right geomechanics resources committed. This commitment needs to be made early in the planning stage of the well construction, and sustained throughout the well delivery cycle. The paper will describe how geomechanics related technology deployment has saved millions of dollars in reducing NPT and achieving business objectives.
PDC Bit Designed for High Lateral and Torsional Stability Significantly Improves Rotary-Steerable Performance in the Middle East
Authors: Barton Steve , Carrington Dominic , Clegg John , Chia Christopher , Garkasi Ali
Published: December 2007

Historic performance in slim hole rotary steerable (RS) applications in the Middle East was held back by severe torsional and lateral vibration issues. A new family of slim hole polycrystalline diamond compact (PDC) bit designs, specifically matched to the rotary steerable systems (RSS) used, has resulted in a dramatic improvement in performance.

The use of mathematically modeled bit performance indices has resulted in a significant improvement in RSS and bit performance while drilling harsh environments in the Middle East where lateral and torsional vibration events are severe. The bit design in question was further optimized by including design characteristics specifically targeted at reducing torsional events. Further, bit hydraulics have been optimized to minimize erosion and maximize borehole quality while matching system operation requirements.

Case studies are presented clearly demonstrating runs with superior performance in the Kingdom of Saudi Arabia (KSA). The field trials clearly demonstrated that significant reduction in torsional vibration and improved side cutting led to superior dogleg achievement. Improvement in lateral stability and resultant bore hole quality led to extended bit and tool life, thus notably improving penetration rate.

The paper concludes that significant performance increases can be achieved by matching the bit design to the RSS, the well geology and the well trajectory. This has resulted in advances in slim hole drilling.
A New Method of Sand Control: The Process and its First Field Implementation
Authors: Aggour Mohamed A. , Abu-Khamsin Sidqi A. , Osman El-Sayed A.
Published: December 2007

A new method of sand control 1,2, which was earlier developed and tested in the laboratory, has been implemented and evaluated in the field. The method is based on a low-temperature oxidation process where a hydrocarbon fluid wetting the sand grains is oxidized resulting in a coke-like solid substance that cements and consolidates the sand grains.

Laboratory development work involved first a series of experiments on small loose-sand packs with the purpose of investigating the effects of control parameters on the quality of sand consolidation and determining the optimum process conditions. Employing the optimum conditions, the process was then tested on a full-scale wellbore model resembling specific actual field conditions. The results of this development work proved that the new method is viable and is potentially superior to existing sand control methods.

The new process was then designed for field-scale applications and was implemented on a well with potential sand production problem. The well was flowing initially at low rates between 200 to 400 bpd and was cutting little sand. Other wells in the field producing at higher rates were experiencing major sand production problems. Following treatment of the well with the new process, the well was produced with ESP at a rate of 4000 bpd without sand production. Close monitoring of the well for more than three months showed no significant rise in sand production.
The Challenges of Deviated Wells
Authors: Krüger Christian
Published: December 2007

A revolutionary intervention technique has emerged allowing mechanical manipulation in horizontal wells in combination with field proven Well Tractor® technology.

As Well Tractor® technology has evolved and confidence has increased in the technology during the last few years, the application of a cost-effective method for opening (and closing) of specific down hole hardware (i.e. valves) as an alternative to existing technologies has emerged. The technology is particularily applicable on offshore installations where the logistical limitations are a major consideration. This article will describe the subsequent applications and the process of developing the technology further.

Tractoring eliminates the constraints of traditional wireline operations by extending the reach of the wireline into the horizontal part of the well and thereby allowing operations to be conducted over the entire length of the wellbore and, if necessary, in a rig-less environment. Additional benefits gained are the elimination of mobilizing heavy equipment, which in turn reduces the number of personnel required to run the operation but most significantly reduces the operational exposure to related safety risks. Furthermore, the equipment required is logistically easier to handle and rig-up time is considerably reduced compared to alternative technologies while providing value-creating solutions.

This paper will present the benefits of wireline interventions, particularly in deviated and horizontal wells, the tractoring solution and case histories exemplifying the advantages of this technology.
Borehole Shape Characterization with Azimuthal LWD Measurements: Evaluation, Applications, and Limitations
Authors: Butt P. , Fareed A. , Ma S. M. , Al-Hajari A. A.
Published: December 2007

Caliper is a fundamental measurement of wellbores. It has significant impacts on decision making regarding well completion and monitoring operations. Traditional Calipers are measured mechanically, thus can not be performed while drilling since they will not be able to survive the harsh conditions of drilling while the bottom hole assembly (BHA) rotates. With logging while drilling (LWD) measurements, several methods have been developed over the years to derive borehole calipers or hole shape indicators from LWD logs. In this paper, we will compare the LWD derived calipers with that obtained from wireline (WL) and summarize the developments, utilizations, and limitations of LWD derived calipers. Factors affecting LWD calipers will also be discussed to help operation petrophysicists for better log data quality control.

Examples will also be shown for using LWD calipers to identify borehole washout, elipticity, breakout, and spiral-hole conditions. Knowing these borehole conditions in real time can help to make action plans to improve drilling practices and reduce drilling risks. After drilling, LWD calipers are used to correct LWD logs for borehole size effects and guide well completions.
Composting: Bioremediation of Soil Contaminated With Weathered Hydrocarbons
Authors: Cecilia Medaura M. , Paula Balla M. , Gutierrez Pablo A. , García de Salamote Inés E. , Garcia Torres Tristán P. , Monzón Azucena , Ercoli Eduardo C.
Published: December 2007

The aim of this work was to evaluate the composting technology in the treatment of soils contaminated with weathered hydrocarbons and drilling cuttings commonly placed in repositories under specific regional conditions.

The composting technology to remediate contaminated soils, consists in the addition of organic material and periodic aeration so that the biodegradation of hazardous organic pollutants and organic matter is favored in a simultaneous process.

In November 2005, a pilot experiment was set up on a location owned by RepsolYPF in the Province of Mendoza, Argentina. Ninety cubic meters of soil contaminated with hydrocarbons were treated under three experimental conditions: two windrows for treatment A (contaminated soil + goat manure, a by-product of the farming activity of the region); two windrows for treatment B (contaminated soil + goat manure + sawdust + sulphur); and two control windrows for treatment C. All the treatments had an aeration system which guaranteed the aerobic process.

Five samples were taken throughout six months of treatment. The variables analyzed were soil physical and chemical parameters, hydrocarbons concentration, microbiological studies and ecotoxicological tests.

The results are encouraging concerning the quality of treated soils: there was a decrease of the toxicity in treatments A and B, an increase in the microbiological diversity, especially for the fungi group, a stimulation of the biological activity (nitrification, humic acid content) and a decrease in the hydrocarbon concentration.

Treatment B turned out to be the most efficient way to obtain a high quality soil. This final product will be used as soil amendment in a well site restoration.
Successes in Curing Massive Lost-Circulation Problems with a New, Expansive LCM
Authors: El-Sayed Mahmoud , Ezz Ahmad , Aziz Moataz , Waheed Arshad
Published: December 2007

The operator controlled losses and a significant salt water kick in a deep gas well using a new dual-action lost-circulation material after fighting losses for 10days. Severe losses were experienced while drilling the Miocene age (Qwassim and Sidi Salim) formations in the Nile Delta region of Egypt. The mud weight was increased to 15.3+ ppge based on pore pressure response until losses started to occur. The losses got beyond 150 bph which hampered operations to drill ahead. Several attempts to cure losses with various commonly used lost circulation formulations were not successful and the choice was either to run casing earlier than planned and compromise the final hole size or attempt a new approach to controlling losses.

This paper will discuss the new approach applied in controlling lost circulation. It involves the use of a "dual-action LCM" that contains multiple-sized particles to enhance fracture tip screenout, along with a synthetic polymer that hydrates in water. When mixed with fresh water and spotted downhole, the polymer can swell up to 400 times its original size. The effectiveness of such treatments help alleviate a lot of the industry troubles by addressing revenue loss from huge mud losses and the non-productive time spent with the rig not drilling ahead.
Custom Designed Water-Based-Mud System Helped Minimize Hole Washouts in High-Temperature Wells: Case History from Western Desert, Egypt
Authors: Bakly Osama , Samir Ahmed
Published: December 2007

It is a common occurrence worldwide to have hole washouts while drilling with water-based mud. There are several reasons for this and until a concerted effort is taken to address the issue, such holes are bound to develop. Some of the problems that large washed-out holes cause are poor hole cleaning while drilling the hole, increased chances of stuck pipe, poor wireline log quality, bad zonal isolation after cementing primary casing strings, and loss of production due to inadequate zonal isolation.

This paper discusses custom-designing water-based systems to address the problem of washed-out holes and wellbore stability. It details the laboratory testing performed on cores and drill cutting samples from the drilled intervals to assess the suitability of appropriate chemicals. The primary study concentrated on understanding the shale inhibition process using water-based fluids. The mineralogical compositions of the shales from the drilled areas were analyzed and tested with various base fluid types and additives.

The recommendations generated from these studies were implemented in high temperature wells drilled by this operator. The results obtained from drilling these wells have been reduced hole wash-outs and stable wellbores.

According to conservative estimates, the problems resulting from shale instability costs the petroleum industry over half a billion dollars per year. The learnings from this paper should help other operators overcome such issues and cut down on non-productive time and expenditures.
Effect of Water Injection on Sand Production Associated with Oil Production in Sandstone Reservoirs
Authors: Essam I. , Wally A.
Published: December 2007

Sand production is a serious problem in many oil and gas assets worldwide. It can affect production rates; it can damage downhole and subsea equipment and surface facilities. Unconsolidated sandstone reservoirs the most susceptible to sand production, which may starts during initial inflow or later, when water breaks through.

Pressure maintenance techniques such as water injection are among the most widely applied secondary recovery processes. When waterflooding is used, early breakthrough at the production well may occur due to reservoir heterogeneity.

There are several possible reasons that may account for rock weakening after water injected water breakthrough:

Chemical reactions between water and rock solids; The changes of surface tension and capillary force; Seepage force resulted from water pressure gradient; Plugging parts of the pay zone.

Based on the actual production history data of Belayim Field wells, which are presented and discussed in the present work, sand production problems detected after salinity of produced water decreased and static bottom hole pressure increased due to water injection effect.

Guidelines to optimize the water injection technique were proposed in the present work as the follows:

Appling compatibility test between formation water and injected water. Sand control technique should be applied or Flow rate reduction after injected water breakthrough. Continues water cut percent monitoring. Appling sand production monitoring and prediction program.
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

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

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

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

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

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

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

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

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

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

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

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

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.
An Early-Time Model for Well Testing of a Hydrate-Capped Gas Reservoir
Authors: Gerami Shahab , Pooladi-Darvish Mehran
Published: December 2007

Natural gas hydrate have been estimated to make up the largest component of fossil fuel resource worldwide. Hydrate reservoirs may be found in different geologic settings including deep ocean sediments and arctic areas. Some reservoirs include a free-gas zone beneath the hydrate, and such a situation is referred to as a hydrate-capped gas reservoir. Gas production from such a reservoir could result in pressure reduction in the hydrate cap and endothermic decomposition of hydrates.

Well testing in a hydrate-capped gas reservoir is a developing art; development of a new model, incorporating the dynamic effects of gas hydrate decomposition, is necessary for realistic and accurate predictions. This paper presents a twodimensional (r,z) mathematical model for a constant rate drawdown test performed in a well completed in the free gas zone of a hydrate-capped gas reservoir during the early-time period of production. Using energy and material balance equations, the effect of endothermic hydrate decomposition appears as an increased compressibility in the resulting governing equation. The Laplace-domain solution for the dimensionless wellbore pressure is derived using Laplace and finite Fourier cosine transforms. The solution to the analytical model was compared with a numerical hydrate reservoir simulator over some range of hydrate reservoir parameters.

The results show that the effect of decomposition on wellbore pressure is substantial. The analytical model can be used for analysis of drawdown tests in hydrate-capped gas reservoirs. Furthermore, it may be used to quantify the contribution of hydrate decomposition on production performance.