bluuebunny/crossref_metadata_2025 huggingface dataset:
Balancing Environmental Tradeoffs Associated with Low Impact Drilling Systems to Produce Unconventional Natural Gas Resources
Authors: Haut Richard C. , Burnett David , Williams Tom , Theodori Gene
Published: February 2011

An environmental scorecard has been developed to determine the tradeoffs associated with implementing low impact drilling technology in environmentally sensitive areas. The scorecard assesses drilling operations and technologies with respect to air, site, water, waste management, biodiversity and societal issues. Low impact operations reduce the environmental footprint of operations by the adoption of new methods to use in (1) getting materials to and from the rig site (site access), (2) reducing the rig site area, (3) using alternative drilling rig power management systems, and (4) adopting waste management at the rig site. The scorecard enables a dialog to be established and maintained among all interested, concerned and affected stakeholders. In this manner, the industry has a new way of seeing itself within the larger network. The scorecard that will be presented in the paper provides the means to demonstrate the connectivity between energy production and the affected ecosystem. The Houston Advanced Research Center (HARC) is leading a consortium effort to investigate the development of low impact drilling systems. The work originated in 2005 and funding was obtained by the U.S. Department of Energy for 2006 – 2009. Additional funding for the effort was obtained through the Research Partnership to Secure Energy for America (RPSEA), industry and environmental organizations. The goal of this project is to reduce the environmental impact of rig operations through integration of low-impact site access and site operations. The paper discusses the scorecard that is being developed. The scorecard methodology presents an ecological understanding of the tradeoffs associated with producing energy. The scorecard methodology was developed through a series of workshops being held with ecologists, botanists, wildlife management experts and others in addition to oil and gas industry experts.
Geostatistical Modeling and Numerical Simulation of the SAGD Process: Case Study of an Athabasca Reservoir With Top Water and Gas Thief Zones
Authors: Bao X. , Chen Z. J. , Wei Y. , Sun J. , Dong C. C. , Deng H. , Song Y.
Published: February 2011

Overlying top water and gas thief zones have a detrimental effect on the Steam-Assisted Gravity Drainage (SAGD) recovery process since steam penetrates into these zones which results in great heat loss. Due to the presence of these top thief zones, recovering bitumen by the SAGD process has become challenging in the Surmont lease of an Athabasca oil sand reservoir.

Previous numerical simulations, laboratory experiments and field production data have demonstrated that oil production and steam-oil ratios tend to decrease as the depletion of top gas continues; also, heat loss to the overlying thief zone will be more significant when a top water zone is present. However, an optimal operating strategy for the full field scale SAGD process with both top gas and top water remains uncertain.

The objective of this paper is to construct a 3D geostatistical model for a Surmont pilot and implement sensitivity study in SAGD simulation aiming at investigating the impact of the top thief zones on bitumen recovery. The major steps involved in the 3D geostatistical modeling process consist of structural, facies and property modeling and uncertainty analysis. Facies-based log-derived porosity, permeability and water saturation are populated into a grid block by Sequential Gaussian Simulation (SGS) in the petrophysical modeling process. Then a static model is further downscaled to finer simulation grids, and a submodel for each single well pair is extracted for the purpose of history match in the STARS™ simulator.

Reasonable history match of oil and water rates has been achieved by calibrating this static model with field production data. The steam chamber pressure and temperature profiles from the numerical model have been conformed to the field data from the observation wells. Sensitivity analysis of the thief zones pressure, thickness and area extension has been conducted to simulate the impact of the top thief zones. Optimization of cumulative steam oil ratios (cSOR) and recovery factors by varying the steam trap control and injection pressure with the top thief zones has been investigated in great detail. Finally, integrated optimization strategies have been developed and tested on a full field-based heterogeneous simulation model.
Corrosion Management of a Worldwide Existing Pipeline Network
Authors: Bonis Michel
Published: February 2011

This paper first describes a semi-quantitative methodology for assessing the corrosion likelihood of existing production pipelines which was developed by the Company and applied over its worldwide operations.

This methodology is based on a quantitative answer to three key practical questions, requiring the involvement of key personnel aware of the past and current operating conditions of each line.

This assessment, carried out on a yearly basis for each subsidiary, is now in its third year and has quickly gained credit from all interested parties, and especially the operating entities of the Company throughout the world.

In a second part a detailed review of the few pipeline failures and of all intelligent pigging results experienced during the last 5 – 8 years is summarized.

It is shown that external corrosion of onshore buried lines and of the aerial section of offshore risers are the two main corrosion issues. A more systematic inspection is the best answer to this problem, although some progress is also needed on the design side. On the other hand, it is shown from numerous cases and examples that internal corrosion of pipelines can be well mitigated over several dozens of years, as long as relevant personnel is aware of (and even preferably "frightened by"…) the possibility of such internal corrosion inside their pipes. As above, there is no better way than inspection to provide this awareness as well as to document the efficiency of mitigation methods.

Last but not least, this review gives access to detailed average corrosion rates for most corrosion modes involved, which can then be used to better assess the Corrosion Likelihood of any pipeline and to adjust inspection frequencies.
Reliable Connectivity Evaluation in Conventional and Heavy Oil Reservoirs: A Case Study From Senlac Heavy Oil Pool, Western Saskatchewan
Authors: Kaviani D. , Jensen J. L.
Published: February 2011

Evaluating interwell connectivities can provide important information for reservoir management by identifying flow conduits, barriers, and injection imbalances. The multiwell productivity index (MPI)-based method is a recently-developed tool to infer interwell connectivity based on injection/production data. Previously, the MPI method worked well when tested on several synthetic cases under ideal conditions. In this paper, we show the application of the method on a field case, the heavy-oil Senlac field in Saskatchewan.

Nonideal but common conditions, such as the unavailability of injector and producer BHP's and short term and frequent producer shut-ins, may have a large affect on the results of the MPI method. By using the similarities of the MPI method and another connectivity evaluation procedure, the capacitance model (CM), we define a new connectivity parameter that is less sensitive to nonideal conditions. Dramatic changes of the mobility ratio in heavy oil fields still affect the performance of the model but, by applying a dynamic multiwell productivity index, we reduce this problem. Temporary shut-in of the producers within the sampling interval also leads to less accurate estimation of connectivity parameters and production rates. By applying an equivalent skin model and using the average rate formula, we can overcome this problem.

Compared to connectivity parameters defined in previous studies, the one defined here is more robust and less sensitive to the specific circumstances that are common in field cases. The dynamic model suggested in this paper helps us to model cases with variable mobility ratios more accurately. Applying the modifications suggested here improves the fit between predicted and actual production. Using the new connectivity parameters in Senlac, we observed good agreement between the connectivity map and the geological features of the reservoir.

The procedures and modifications described in this paper enable us to use the MPI method more effectively in field cases with common nonideal conditions, including heavy oil waterfloods. Insensitivity of the model to changing well conditions provides a more versatile tool to analyze field data. Furthermore, if we choose to use the CM instead of the MPI, we find that using information from the MPI can benefit the application of the CM. Applying these approaches, we can have a more reliable understanding of the reservoir heterogeneity and quick prediction of reservoir performance to optimize the waterflood.
Record-Setting Horizontal Pilot Wells Drilled and Completed to Establish Feasibility of Developing Giant Offshore Field from Artificial Islands
Authors: Jorden John , Keller Stu , Al Junaibi Hamad Saleh
Published: February 2011

This paper summarizes the planning and execution of the well construction and completion of two pilot wells in a giant oil field offshore Abu Dhabi. These wells are an injector-producer pair batch drilled by a jack-up rig from a wellhead platform tower (WHPT). The wells have measured depths of approximately 20,000 ft and a 10,000-ft horizontal reservoir section. The main objective of drilling these wells is to establish the feasibility of developing the field using extended-reach wells drilled from artificial islands instead of the current scheme of using WHPTs.

The wells set a number of records and firsts, including: Longest measured depth well drilled offshore Abu DhabiDrilling the longest horizontal reservoir interval offshore Abu DhabiInstalling the world’s longest high-hole-density preperforated completion linerFirst use of non-aqueous drilling fluid (NAF) offshore Abu DhabiFirst use of a scale-preventing sodium chloride/sodium bromide reservoir drill-in fluid offshore Abu Dhabi

One of the main drilling challenges was the need to drill a weak shale formation at high angle (> 60 degree) and smoothly land the well at a 90-degree inclination in the target reservoir. This was addressed by performing a Fast Drill Borehole Management study to identify the optimum drilling parameters (e.g., mud weight, flow rate) and by use of NAF as well as optimum operational practices. This first use of NAF offshore Abu Dhabi required extensive rig modifications and the transport of cuttings to shore for cleaning and disposal.

One of the main completion challenges was to compartmentalize the 10,000 ft reservoir interval into segments for reservoir management. This was achieved by using a pre-perforated liner run with ten swell packers in each well. The liner perforation size and pattern were designed to ensure effective stimulation access while minimizing risk of liner damage due to installation loads.

Another challenge was acid stimulation of the completion interval which had a pore pressure greater than 1.2 sg (10.0 ppg) due to offset injection wells. To address the stimulation challenges, a 22,000-ft, 2-3/8-inch coiled tubing string was designed and fabricated.

The paper addresses a number of aspects of the planning and execution of these ERD pilot wells, including Well design, including well path planningDrilling fluidsRig modificationsCompletion designStimulation planningBatch drilling operationsNAF cuttings managementDirectional drilling performanceCompletion liner runningPlans for future pilot wells
Natural Gas Potential in the Saint Lawrence Lowlands of Quebec: A Case Study
Authors: Lavoie Jean-Yves , Marcil Jean-Sebastien , Dorrins Peter K. , Lavoie Jeremie , Aguilera Roberto
Published: February 2011

Since the announcement made in April 2008 concerning the shale gas potential of the Southern Quebec Lowlands, almost 15 new wells have been drilled in the area. The calcareous and organic-rich Middle Ordovician Utica Shale is the main target of this recent exploration effort. Current knowledge of the area's geology have led operators subdivide the shale gas potential into different play types. To date, most operations have been performed in approximately 1/3 of the shale basin in the medium to deep thermogenic shale gas play (1,000-2,000 meters), located in the central part of the Saint Lawrence Lowlands. With OGIP estimates ranging from 120 to 160 Bcf per section, the deep play is considered to be promising. Current efforts focus on determining the highest gas prone unit within the Utica. The remaining 2/3 of the shale basin has not been largely tested yet, but the potential remains promising.

Based on exploration work carried out over the past five years in Southern Quebec, four other play types have been described: 1) shallow to medium depth thermogenic shale gas; 2) overthrusted shale gas; 3) biogenic shale gas; 4) Intra-Appalachians sub-basin shale gas. They are less explored than the deep shale play, but also present interesting potential.

This paper describes the above mentioned plays using basin geology, shale mineralogy, organic matter type, gas geochemistry, structural style and infrastructure access. The characteristics of the above plays are reviewed from geological, geochemical, structural and production perspectives. Results of evaluations using the concept of flow units, and volumes of original-gas-in-place calculated by various organizations are compared with a recent evaluation using the Petroleum Resources Management System (PRMS).

It is concluded that there is promising hydrocarbon potential in the Saint Lawrence Lowlands of Quebec that continue to stimulate operators to pursue the exploration and development of these plays.
An Experimental Investigation Of In-Situ Combustion in Heterogeneous Media
Authors: Awoleke O. G. , Castanier L. M. , Kovscek A. R.
Published: February 2011

In-situ combustion (ISC) is an intriguing yet complex method of enhanced oil recovery due to the interplay of air flow and oil reactivity. This paper presents the results of a recent experimental effort to shed more light on the ISC process by investigating the effects of different scales of porous medium heterogeneity on ISC. We probed the effects of pressure, temperature, injection rates and matrix properties on the combustion of Middle-Eastern 19.7° API and a Californian 16° API crude oils. The experimental perspective includes both oil oxidation kinetics and combustion-front dynamics in a 1-m long combustion tube. After establishing successful combustion in homogeneous media, we proceeded to investigate the effect of heterogeneity on the ISC process by conducting combustion tube runs in a gravity-stable mode. From the experimental data, pre and post-burn CT scans, and postmortem analysis, we deduced the effect of both small and large-scale heterogeneities on the spatial and temporal propagation of the combustion front. The combustion front traveled unhindered through sections of the combustion tube containing heterogeneous packing with length scales on the order of centimeters. On the other hand, it was more difficult to obtain successful front propagation in media with heterogeneities on the order of tens of centimeters. The ISC process was probably challenged by the relatively fast transport of air through high-permeability zones and the relatively slow transport of the much-needed air through low permeability sandstone thereby effectively starving the burning front of oxygen, and extinguishing the process in this case.
Seismic Source Parameters Optimization in Shallow Water Area Offshore Abu Dhabi, U.A.E.
Authors: Ishiyama Tomohide , Painter Derrick , Belaid Kamel
Published: February 2011

Seismic source parameters are one of the important specifications for a seismic survey. Conventional thinking is that larger sources produce higher energy, and thereby improve data quality. However, in shallow water areas offshore Abu Dhabi, United Arab Emirates (U.A.E.), the source size is limited due to operational constraints such as shallow water depth and several scattered production facilities.

To address these issues, a pilot seismic survey was acquired in a shallow water area with the main objectives: to determine data quality versus source parameters; and to optimize source parameters for future seismic surveys. In this survey, several datasets were acquired with different source parameters, however, using the same source vessel and air-gun array. Then, data quality for each dataset was evaluated at various processing stages.

We show that shorter shot-point interval (SPI) and appropriate processing, e.g. noise attenuation in a domain with a closer trace interval, could compensate for a lack of source energy, then even a small source could achieve the required data quality with the aid of suitable SPI and processing. The results should encourage investigating even smaller sources which are easier for the operations and friendlier to the environment.
Developed Approach for Better Understanding of Low Resistivity Pay Carbonate Reservoirs
Authors: Obeidi Adel , Aryani Fatema Al , Amoudi Mohsen Al
Published: February 2011

Some of the Middle East UAE lower Cretaceous Thamama Carbonate reservoirs are characterized by low resistivity pay phenomena, on which log analysis results in high water saturation computation; on the contrary, production tests confirm dry oil.

The Sedmintological investigation on thin sections have shown significant percentage of Micro-porous (occluded porosity or non-efficient porosity) network traps irreducible hyper-saline formation water which responds to a low resistivity, even if the oil is occupying the larger size of porosity (efficient porosity).

This paper presents a simple and cost-effective approach for better identification and evaluation of low resistivity pay carbonate reservoirs. The approach utilizes the pulsed neutron capture log (PNCL) in real-time logging in proper identification and formation evaluation in these reservoirs through case studies in the Middle East-UAE Carbonate reservoirs.

Through number of wells that have recently been drilled using different types of mud and were logged by LWD PNCL; the results have clearly shown the benefit of minimizing evaluation uncertainties compared to those logged without LWD PNCL.

For decades, the combination of conventional logs i.e. neutron, density and resistivity are undoubtedly proven technologies to evaluating homogenous reservoirs. Unlikely, accurate determination of Petrophysical parameters and water saturation evaluation would rather be difficult to show especially in so-called low resistivity pay reservoirs. Since the PNCL (Sigma log) provides a resistivity independent water saturation evaluation, the PNCL has become an integral part of the evaluation program in these low resistivity pay reservoirs, particularly using OBM with relatively high rate of penetration, so that well bore surrounding environment would not be greatly altered (minimum invasion). LWD drill and wipe passes evidently demonstrate that the different between logs can be caused only by reservoir fluid change.
Multistage Fractured Cardium Oil: Studying Geology and All of the Production and Stimulation History Thus Far
Authors: Leshchyshyn T. T.
Published: February 2011

As the industry has unlocked vast new resources in North America with multistage fractured horizontal wells, an immense push has occured in terms of applying these new technologies to new plays. In the last 3 years, there has been an immense development in the Cardium tight oil play in Alberta, Canada, as commodity prices have encouraged a shift to oil exploitation whereever possible. A variety of operators and service companies have employed many differing techniques which have evolved over the years, to attempt to maximize Cardium oil production and reserves.

ALL public well files for ALL fractured horizontal wells have already been collected from the public realm regardless of the operator and service company. leading up to the abstract submission date with select wells added up to manuscript deadline date. These files are currently being reviewed and tied to production to establish empirical results and evolution in the exploitation of this play. Factors currently being examined are isolation technologies, stage spacing, frac fluid selection, proppant selection as well as a variety of other information.

A large amount of geological information will be reviewed and presented in order to understand the production expectations as a part of a regional study of various geological properties. When possible, a combination of geological and stimulation information will be examined together.
Whole Core Versus Plugs: Integrating Log and Core Data to Decrease Uncertainty in Petrophysical Interpretation and STOIP Calculations
Authors: El Din S. Serag , Dernaika M. R. , Al Hosani I. , Hannon L. , Skjœveland S. M. , Kalam M. Z.
Published: February 2011

Most carbonate reservoirs are commonly characterized by multiple-porosity systems that impart petrophysical heterogeneity to the gross of reservoir interval. Hence, the specific types and relative percentages of pores present, and their distribution within the rocks, exert strong control on the production and stimulation characteristics of carbonate reservoirs.

The impact of heterogeneity on core and log measurements is assessed. The challenge is to determine the reliability of relatively small scale properties measured by a log or core to the large scale reservoir property. A related question is one of reconciling the variability seen in high resolution (small volume of investigation) measurements (e.g. core plugs), with the variability in relatively low resolution (large volume of investigation) measurements (e.g. wireline log).

Routine and SCAL laboratory measurements on carbonate core samples from prolific reservoir in Abu Dhabi. The measurements were conducted on different scale samples ranging from small trims to full diameter whole core samples. Porosity and permeability obtained from small trims, plugs and whole core samples were compared with log data to study the impact of the measured volume on the results. Electrical property measurements were performed on 1.5" diameter plugs and 4" diameter whole core samples to evaluate the impact of heterogeneity and volume scale on cementation factors which are essential for proper petrophysical interpretation and saturation calculations.

Different scale measurements showed variations in both Routine and SCAL data and emphasized the importance of the whole core measurements in representing reservoir heterogeneity which could be used to better evaluate resistivity logs. Plug scale Poroperm data; however, were important in capturing higher degree of reservoir heterogeneity. The better integration between core and log data and the use of the right electrical parameters in petrophysical interpretation tends to minimize the uncertainty in STOIP calculations.
Fit-for-Purpose Sealant Selection for Zonal Isolation in HPHT Deep Tight Gas Wells
Authors: Al-Thuwaini J.. , Emad M.. , Ekpe J.. , Jaffery M.. , Ong D.. , Taoutaou S.. , Ahmad B..
Published: February 2011

Zonal isolation has extreme significance in the construction quality and life of a well. Achieving zonal isolation in deep high- pressure, high-temperature (HPHT) gas wells is a challenging task, and these wells need more attention to achieve zonal isolation than conventional oil or gas wells. In addition to following primary industry best practices, the selection of a cement system appropriate for the environment of the well is very significant. Trapped gas and oil between production and intermediate casing (abnormal annulus wellhead pressure) has been globally recognized as one of the serious challenges facing drilling and production operations. The issue is becoming even more serious since wells are aging and the integrity of the casing portion below the well head is increasingly affected by the shallow-water corrosive environment. The potential safety and environmental hazards of the abnormal annulus pressure, have encouraged LUKSAR (Lukoil Saudi Arabia Energy Limited) to review the current drilling and cementing practices, with the goal of minimizing the impact of the problem, thus improving well life cycle and reducing the frequent work-over interventions. The general guidelines set to resolve the problem focused on eliminating potential leakage paths in the completion and casing strings and emphasized the quality of the primary cementing, especially for casings set on the aquifer zones and production casings.

This paper discusses case histories and selection criteria for the different cement systems. It shows how high-performance lightweight sealant across weak zones, fiber-based sealant technology when lost circulation prevails, self healing sealant system where zonal isolation is extremely important, and flexible and expanding sealant for frac candidates are chosen for providing and maintaining well integrity in these extremely remote and challenging HPHT wells.
New Approach to Improve the Horizontal Drilling Reach
Authors: Vestavik O. M. , Syse H. , Hole O. , Aleksandersen J.
Published: February 2011

In order to improve the cost efficiency of petroleum exploration and production, it is required to develop improved technology. The Reelwell Drilling Method (RDM) is a multi purpose drilling method with a unique arrangement for Extended Reach Drilling and Managed Pressure Drilling. A conventional drill string with a special inner string forms a dual concentric drill string, which is used to remove drill cuttings from the bottom of the well. A separate hydraulic fluid system is used to push the drilling assembly forward using fluid pressure from the surface.

The development of RDM started in 2004 and has since then been through several full scale operations in Norway. In 2009 RDM was successfully used to directional drill the 8 ½" section of a land well. The proof of concept and the practical application on conventional drilling rigs has been verified, as well as the features of the system, such as:

- Managed Pressure Drilling (MPD) – Unique isolation using a new downhole valve solution. - Very precise well pressure management and flow control (gain/loss). - Efficient hole cleaning and cutting removal from wellbore - Efficient hydraulic traction and WOB control.

The RDM is currently planned to be used for drilling horizontal wells in Canada. The potential to increase the reach for horizontal wells is here further discussed.
Feasibility of In-Situ Combustion in the Mature SAGD Chamber
Authors: Oskouei S. J. , Moore R. G. , Maini B. , Mehta S. A.
Published: February 2011

Steam Assisted Gravity Drainage, SAGD, is a commercially successful bitumen recovery method that has transformed some of the vast Canadian oil-sand deposits into recoverable reserves. Several SAGD projects have been developed in Northern Alberta in the past few years and many more are in the planning stages. As the projects mature, new operational problems are revealed demanding new solutions. Due to operational restrictions, it is almost impossible to have the same growth rate in all steam chambers in a SAGD pattern. Hence, interference between a mature chamber and an adjoining immature chamber can become a problem. Steam leakage from the immature chamber into the mature chamber, reduces the thermal efficiency of the project and requires a solution to prevent the steam dissipation.

Filling the mature chamber with combustion gases is a possible solution for this problem. Carrying out in situ combustion in the mature chamber would not only create the needed combustion gases in the chamber but could also recover a substantial part of the residual oil in the mature chamber. It is also likely that the combustion would create a reduced permeability coke zone around the mature chamber, thus isolating it from the rest of the reservoir.

To evaluate the merit of this idea, an elevated pressure experiment was conducted using a two dimensional physical model. Conventional SAGD process was conducted in the model to develop a large steam chamber. Air was then injected through a horizontal well near the top of the model, into the SAGD chamber and a combustion front was established around the air injection well. By operating combustion in the depleted chamber, residual oil was mobilized and produced. The oil recovery was increased by more than 20% over the SAGD operation. Initiation and propagation of combustion was confirmed by a large increase in the temperature in the combustion zone. After unpacking the model, it was found that a coke layer was formed around the perimeter of the chamber.
Exploiting Natural Fracture and Fault Fairways in the Jean Marie Carbonate Platform, N.E. British Columbia
Authors: Wierzbicki R. , Todorovic-Maranic D.
Published: February 2011

This presentation will review the nature of fractures in the Jean Marie from thin section to the seismic scale and focus on the seismic methods used to detect and exploit these high permeability fairways. Drilling results and production indicators of fracture flow will be reviewed, and the controls on fracturing discussed.

The Jean Marie carbonate is an Upper Devonian aged carbonate platform that developed on the western margin of North America. Gas is regionally trapped in moderate porosity and low permeability stromatoporoid-renalcid limestone reef mounds and limestone intermound sediments. The pool has been developed using underbalanced horizontal drilling to minimize damage to the fine pore system in this underpressured reservoir. Advanced seismic techniques are being used to detect porosity zones and high permeability fairways which increase deliverability and recovery of gas from the Jean Marie carbonate. Variable well productivity has been observed in similar facies, as has high productivity in low porosity rock.

In the last five years, in the Kotcho area, Encana has been targeting natural fracture/fault networks in the Jean Marie. These zones of fracture enhanced and diagenetically altered carbonates have better permeability, and often better porosity. The fracture networks appear to have controlled the distribution of hydrothermal fluids which enhance the porosity and permeability of the carbonate via dissolution and recrystalization. Horizontal wells that encounter fractures generally have better deliverability and greater associated reserves. The use of seismically derived porosity and fracture detection techniques has improved the well planning and the frequency of discovery of higher permeability/deliverability zones.

Fracture detection is an important component in the development of the understanding of the permeability system in a reservoir. Fractures and faults can be high permeability production zones, or thief zones for fracturing programs, or barriers to flow if they are cemented shut. The techniques used by Encana in the Jean Marie can be applied to other reservoirs and other lithologies.
Non-Cemented Casing Tieback String Reduces Expense and Risk in Deepwater Operations
Authors: Hinkie Ron
Published: February 2011

The method of anchoring a tieback casing string using cement has been well documented. Industry standards for installing a tieback casing string usually have called for placing cement around the outside of the tieback casing string to provide a barrier against the potential of sustained surface casing pressure (SCP). The cement also is used to anchor the tieback casing string into the polished-bore receptacle during production. After cementing the tieback casing string, a cleanout trip is required to clean the inside diameter of the casing and to remove the landing collar and cementing wiper plugs.

A recent application in deepwater Gulf of Mexico (GOM) allowed a major oil and gas company to perform a step change in technology that enabled the operator to perform the function more rapidly and at reduced expense. Swellable packers were used instead of cement, providing a novel, cost-saving and risk-reducing approach.

This paper will discuss the use of swellable technology as an alternative method for anchoring a tieback casing string. This concept allows the operator to isolate potential downhole pressure away from the surface and to anchor the tieback casing string during production. By using swellable technology, no cleanout trip is required, which provides a substantial cost savings for deepwater operations. The unique approach also reduces the risk to the casing and drilling string from the removal of the cementing wiper plugs and the landing collar. The case history will provide the details of the new application and how it improved cost efficiency and enhanced operational safety.
Effect of Solution-Gas-Oil-Ratio on Performance of Solution Gas Drive in Foamy Heavy Oil Systems
Authors: Busahmin B. S. , Maini B. B.
Published: February 2011

Foamy oil flow occurs in primary depletion of heavy oil reservoirs as has been demonstrated in many laboratory experiments. It is thought to be an important recovery mechanism in several heavy oil reservoirs in Canada and Venezuela, which have shown higher recovery factors compared to what is expected from the normal solution gas drive theory. This work investigates the effects of several process parameters on oil production rate and recovery factor in foamy solution gas drive.

The parameters examined included gas-oil-ratio (GOR), saturation pressure, the rate of pressure depletion and the drawdown pressure. GOR was varied independent of saturation pressure by using different gases, namely, methane, ethane and carbon-dioxide. Each foamy oil system was fully characterized by measuring gas oil ratio, oil compressibility, live oil viscosity, surface tension and foam stability. A total of 10 solution gas drive experiments were carried out in 2-meter long sand-pack equipped with several intermediate pressure taps using different solution gases and varying pressure decline rates.

The results show that the foamy solution gas drive performance is affected by solution gas-oil-ratio in a counterintuitive manner. The oil recovery decreased with increasing gas oil ratio at fixed saturation pressure. At the same rate of pressure depletion, higher oil recovery was obtained with methane saturated oil than with carbon dioxide saturated oil. Ethane, which had the highest solubility, provided the lowest recovery factors. It was also found that the oil recovery factor did not decrease significantly when the saturation pressure was decreased from 3,500 kPa to 2,100 kPa.

An analysis of all 10 depletion tests revealed that the most important factor that affects the oil recovery performance was the drawdown pressure, which was defined as the difference between the average sand-pack pressure and the production port pressure. Results obtained with different solution gases and widely varying depletion rates fell on the same trend line when the final recovery factor was plotted against the average drawdown pressure applied during the depletion.
New Insight on the Depositional Environment and Facies Atlas of Aptian in a Super Giant Carbonate Field in the Middle East
Authors: El Wazir Zinhom , Vahrenkamp Volker C. , Mueller Klaus , Al Madani Noura , Al Shekaili Fatema , Messisha Abdelmalek , Bijaripour Aita , Funk Erich
Published: February 2011

The 3D architecture of flow units is a key parameter influencing production and recovery from oil reservoirs. Depositional facies and their 3D stacking patterns are commonly fundamental building blocks of flow units. Hence, the recognition of facies, and their placement in conceptual depositional environments is the basic requirement to establish 3 dimensional architectural models of reservoirs.

In order to establish facies, facies stacking patterns and the 3D architecture of a super giant field contained in the Aptian in onshore Abu Dhabi , detailed sedimentological and petrographic core description have been carried out using about 13000 ft of core from a total of 49 cored wells. In total 27 facies have been established using fabric and bio content. They have been placed into conceptual depositional models following an evolving platform to basin topography during transgressive, early highstand and late highstand phases of carbonate platform development during the Aptian. This paper presents a comprehensive facies atlas that contains for each facies a detailed description of fabric and bio content, core and thin section pictures, petrophysical summaries and an interpretation of depositional environment. The large areal distribution of core coverage over more than 800 square km paired with the location of the reservoir transgressing platform interior to basinal settings ensures a comprehensive coverage of facies typical for most of the Aptian.

The study developed an updated and unified facies scheme embedded in the existing interpretation of the depositional environments and high resolution sequence stratigraphy, and completed the core facies scheme definition which is understood as a fundamental criteria for the population of 3D static and dynamic model, in order to effectively enhance future reservoir development.
Supercritical CO2/Methane Relative Permeability Investigation
Authors: Sidiq H.H.. H. , Amin R..
Published: February 2011

This paper presents extensive laboratory results of unsteady state displacement of methane by super critical carbon dioxide SCO2 in consolidated reservoir core plugs. The fluid flow of the both phases is presented in terms of relative permeability using explicit methods. The main objective of this study was to investigate the feasibility of SCO2 injection for enhanced gas recovery for a newly discovered gas field situated in the North West Shelf of Western Australia.

The core-flooding experiments of SCO2-methane were carried out on three short plugs and one long vertical sample. The impacts of various parameters were broadly studied on the recovery efficiency and gas multiphase flow at pore scale. These were pressure, temperature, composition, injection-rate, and permeability heterogeneity. Results indicated that the recovery factor at CO2 breakthrough is a function of in situ gas composition, injection rate, and pore pressure. In contrast temperature, absolute permeability and core position factors moderately affected the recovery factor.

A new power model has been developed for interpolating experimental gas-gas relative permeability data. This model can accurately account for subsequent gas compositional changes during the displacement process.
Addressing Reservoir Heterogeneities in the Development of Upper Jurassic Carbonate Reservoirs, Offshore Abu Dhabi
Authors: Lehmann Christoph T. , Al Hosany Khalil I. , Matarid Tarek , Sayed Mohamed I.
Published: February 2011

Detailed seismic interpretations and an integrated reservoir characterization study were performed on a field offshore Abu Dhabi which reveals new insights into reservoir heterogeneities, both laterally, as well as vertically. The new interpretations provide the team with new insights into the subsurface heterogeneities and address them during the development plan.

The Upper Jurassic carbonate reservoirs, offshore Abu Dhabi, exhibiting heterogeneities on different scales. The lower reservoir section is a large shoaling-upward sequence with an upward increase in reservoir properties. Smaller-scale sequences are superimposed and define the major flow units. Stromatoporoids build-ups or layers are intercalated in the upper part of the lower reservoir section. These layers are characterized by vuggy porosity and the intervals exhibit significant higher permeablities. The upper reservoir section is characterized by meter-scale sabkha cycles composed of mixed carbonates and evaporites. The major reservoir units are separated by thick continuous evaporite units which are regionally continuous. The smaller scale sequences which are the major flow units might be separated by evaporite layers or dense carbonate intervals. Reservoir quality in the major flow units is controlled by dolomitization and anhydrite cementation and further compartmentalizes the reservoir. Understanding the spatial distribution of these reservoir heterogeneities (depositional and diagenetic) is crucial for the development plan.

Reservoir heterogeneities, lateral and vertical, have a major impact on the placement of producers and water and gas injectors. Changes in reservoir quality create sweet spots but also lower productive interval in the individual flow units. The use of intelligent wells and new completion strategies will be also applied to monitor and control early gas and water break through within the field. Our current understanding of the reservoir heterogeneities, therefore, helps us to mitigate some of the subsurface uncertainties. These heterogeneities will be further appraised and mitigated during early field development.
Mishrif Diagenetic Trapping Potential in Western Onshore Abu Dhabi
Authors: Taher Ahmed , Azzam Ibrahim , Abdulla Noor Ali , Witte Johan
Published: February 2011

A diagenetic trapping style is proposed for an oil accumulation found in the Mishrif Formation in the southwestern part of onshore Abu Dhabi.

A diagenetic trapping scenario, which assumes updip sealing by cementation is much riskier than a structural trapping scenario, but has large up-side potential. Oil accumulations in diagenetic traps represent an equilibrium state between buoyancy forces trying to move oil through rocks and capillary pressures in the low permeable layer that resists this movement. The only requirement for a diagenetic trap to exist is that the capillary pressure in the sealing formation is greater than the migration (buoyancy) force in the reservoir rock. In addition to that, smaller pore throat sizes in the sealing formation and larger oil molecules, for instance the product of an early oil migration stage, in the reservoir, can enhance the sealing capacity of the stratigraphic trap and result in bigger oil columns.

The potential of this particular Mishrif prospect was assessed on the basis of regional analogs and a geological model was developed. The prospect was matured by the acquisition of a 3D seismic survey in 2004 (Fig. 1), with the aim to delineate the limits of the stratigraphic trap. A detailed seismic reservoir characterization study was carried out and porosity maps were prepared on the basis of a calibrated acoustic impedance cube. Seismic attributes were generated with the aim to detect the fault/fracture patterns in the area.

The Mishrif stratigraphic trap in southwestern onshore Abu Dhabi is highly prospective since it is located adjacent to the mature Shilaif kitchen in the Ghurab Syncline (Rub’ al Khali Basin). The Shilaif source rock, which is time equivalent to the Mishrif shelf facies (Fig. 2), was deposited under restricted water circulation and anoxic conditions. Basin modeling suggested that the timing of hydrocarbon charge from this kitchen into the Mishrif reservoir started as early as Late Miocene.

The Mishrif play prospectivity evaluation, including the detailed and integrated geological model and 3D seismic interpretation will guide future appraisal drilling. In addition, the knowledge gained from this study can serve as a basis for further exploration activities related to unconventional trapping styles in the Mishrif Formation.
Carbonate Reservoir Complexity Resolving through Static and Dynamic Data Integration for FFDP Optimization
Authors: Al Meamari Ayesha , Al Shekaili Fatema , Assreti Elamari , Al Nuaimi Nawal , Jasser Majdolin , Mueller Klaus
Published: February 2011

A giant Middle East Carbonate Field is producing since 47 years with more than 700 borehole penetrations. The reservoir is 400ft thick of Lower Cretaceous shallow water carbonates with large intra-shelf basin. The reservoir has complex internal architecture due to the formation and in fill of the Basin.

Although connected to a large aquifer, with production the reservoir pressure declined by almost a 1000 psi within 10 years. Peripheral injection started to restore the reservoir energy and sustain production. Injected water in the periphery naturally went into the most permeable layers causing uneven sweep both aerially and vertically. Especially in the progrades with sequence of porous/dense intervals and typical permeability range between 0.1-10 md, oil production could not be sustained with peripheral injection, resulting in dedicated pattern injection schemes.

The reservoir unit, subject of this paper, is geologically complex due ro-grading and oblique clinoforms intervened by dense subunits, overlain with high permeable unit. The unit was developed in the last 5 years using gas-injection line-drive in the northern flank (permeability less than 2 md) and inverted 9-spot WAG patterns. Production from the area has not reached the target rate based on simulation. In addition, some injectors are suffering from low injectivity and based on pressure response compartmentalization is an issue.

This study integrates newly acquired data through additional wells, 3D seismic reprocessing, updated stratigraphy studies, better understanding of the porous/dense correlation, updated static model and dynamic performance data (well testing, transient surveys, saturation logging, production logging, etc…).

Main conclusions of the study include: Lack of connectivity is largely attributed to completing wells in different clinoforms.Producers and injectors do not have uniform profile across the horizontal section.Injected gas in the WAG is not contained and has percolated to the upper unit.

As result of integrating the static and dynamic data, the newly developed model will be utilized to optimize well trajectories, reduce pattern size and study the merits of continuing the WAG injection scheme.
Execution of Brownfield Projects
Authors: Al-Khaledi Sadoun , Waheed Farrukh
Published: February 2011

While the Greenfield projects are considered much easier to execute, both execution and commissioning of Brownfield projects constitutes a major challenge to the oil and gas industry. Still the oil industry due to various financial and operational constraints is continuously pursuing the constructing and commissioning of more and more Brownfield projects. The challenges of executing Brownfield projects are not only confined to the planning, construction activities as far as the Contractors are concerned but it presents a significant challenge to the asset owners for accommodating various construction activities within an operational facility that can have significant integrity issues. Project completion schedule, production downtime and facilities outage also presents a challenge to both the construction contractor and the asset.

This paper will present a case study on one of the major Brownfield project that was recently constructed and commissioned in Kuwait Oil Company (KOC). Although the project significantly enhanced the Company production capacities and capability, however lot of efforts and dedication was required for successful completion of the project. The extend of the construction activity can be comprehended by the fact that all 14 Oil/Gas Gathering centers in greater Burgan fields were upgraded with the addition of new production facilities like gas compressors, oil/gas separators with water treatment units, crude dehydration and desalting facilities and re-location of all critical hydrocarbon piping from underground piping to above ground.