bluuebunny/crossref_metadata_2025 huggingface dataset:
Proppant Selection and Its Effect on the Results of Fracturing Treatments Performed in Shale Formations
Authors: Terracina J. M. , Turner J. M. , Collins D. H. , Spillars S. E.
Published: February 2011

Since the introduction of hydraulic fracturing, the industry has been attempting to establish laboratory testing parameters that assist operators and service companies in their effort to select the optimum proppant for a particular field application. An example of this effort is the development of the "long-term baseline conductivity laboratory test" for proppants. While this test is a huge leap forward in subjecting proppant to simulated downhole conditions, it still does not adequately address many additional factors that can impact the effectiveness of the proppant such as:

Proppant fines generation and migration in the fracture Proppant resistance to cyclic stress changes Proppant embedment in the fracture face Proppant flowback and pack rearrangement in the fracture Downhole proppant scaling

Most proppant choices are currently based on which one has the highest baseline conductivity, cost, and availability. While this approach seems logical, it runs the risk of overlooking or under-valuing other critical factors effecting proppant performance in downhole environments.

To better define what constitutes the most effective proppant for a particular application, field cases will be presented that focus on the impact of proppant selection in a number of wells completed in various shale formations. The analysis will examine the production history associated with a variety of proppant choices. In an effort to better understand the production results, a series of lab tests will be performed on the proppants utilized in the field cases. These tests will attempt to establish how these factors (such as proppant fines, cyclic stress, embedment, proppant flowback, and scaling) could be used to explain and support the results of the field cases.
Discrete Modeling and Simulation on Potential Leakage through Fractures in CO2 Sequestration
Authors: Huo Da , Gong Bin
Published: February 2011

Natural or injection induced fractures, and abandoned wells with no complete seals are the main sources for CO2 leakage after sequestration. Based on research from various scientific studies, pilot CCS programs and commercial CCS projects, formations and/or cap rocks with fractures may have significant leakage problems thus degrade CO2 sequestration results. Modeling and Simulation of CO2 flow in fractured systems is crucially important for CO2 storage location selection and leakage risk evaluation.

With continuous improvement in fracture characterization, Discrete Fracture Modeling (DFM) is becoming more and more widely used as it can effectively resolve the fracture geometry with much less cells. Recent works from Gong et. al have presented successful application of DFM to large-scale compositional simulations for a gigantic carbonate reservoir. In this work, DFM work flow is applied for simulations on CO2 sequestration for the first time. Fractures are represented explicitly and individually as planar surfaces under an unstructured grid system. Transmissibility between each pair of adjacent cells is calculated and flow simulations are performed by a general connection-list based reservoir simulator.

Several examples including several 2D systems with or without fractures and a system with strong capillary pressure effects are demonstrated. Simulations on systems with fractures in CO2 injection formation versus in cap rocks are compared. Results have shown that the existence of mudstone layers could prevent injected CO2 from leaking outside the aquifer when no fractures are present. While vertical fractures intersecting with mudstone layers will cause significant leakage increase as the fractures form extremely preferential pathways for CO2 transport. Capillary forces also enable us to store CO2 in target aquifer for a long timeframe as it could help trap the residual phase CO2. In comparison with conventional simulators using structured grids, this work provides typical speedups of 3-10.
Petroleum Producer Risk Profile Analysis: Does Risk-Taking Pay
Authors: Virine Lev
Published: February 2011

Petroleum producers have different tolerance towards risks. When some predominately junior producers focus on exploration, development, and production in plays with higher risks, others often curtail exploration and development in time of economic uncertainties or tend to focus on the developed plays. Producer's attitude towards risks should be consistent with corporate strategy. Decisions regarding different exploration, development, and production projects should be made based on consistent assessment of risk attitude. The challenge is to elicit company's preferences towards risks and apply this information to the corporate decisionmaking. This paper describes methodology of the risk attitude analysis for the petroleum produces. In order to numerically assess producer's attitude towards risks a mathematical model has been developed. The model employed a number of key performance indicators tailored to assess risk attitude. Different weights were assigned to each indicator. Composite risk attitude score for each producer was calculated based on key performance indicators. This score represents producer's risk attitude and can be used in decision tree analysis as well as in multi-attribute utility analysis. The proposed methodology was applied for the comparison of risk attitude of different independent gas producers operating in North America. The positive correlation between risk taking and company's performance can be demonstrated under certain conditions, such as access to financing and technology. The proposed methodology can be applied to eliciting of risk attitude of the petroleum producers for the purpose of improving corporate planning process.
Quantitative Ranking Measures Oil Field Chemicals Environmental Impact
Authors: Jordan Andy , Daulton Dan , Ann Cobb Jo , Grumbles Thomas
Published: February 2011

Environmental stewardship has been and continues to be a critical component of the oil and gas industry, as exploitation of shale and other unconventional gas reservoirs requires large volumes of water for economic and efficient production. Evaluating and communicating the hazards of chemicals is done in a highly variable manner across the world. However the recent adoption of the Globally Harmonized System of Classification and Labeling of Chemicals (GHS) by multiple Global regulatory bodies has brought international consensus to hazard criteria and definitions. This system is being implemented with REACH in the EU. In the US OSHA has just proposed the GHS criteria as the basis for modifying their hazard communication regulations. This standardization ensures information about hazards and toxicity of chemicals is more universally available, to enhance protection of human health and the environment during handling, transportation and use. It is this scheme that we are beginning to utilize as the basis for the ranking of products and systems.

This paper will describe the evaluation and implementation of a practical and quantitative process of ranking well servicing products based on their safety, health and environmental impacts. The ranking allows operators to select and use products that best fit their environmental stewardship goals, and provides scientifically sound tools for better research and development, and educational efforts.
Successful Thermal Recovery of Heavy Oil From an Ultra Tight Reservoir Renews Development of the 100-Year-Old Orcutt Oil Field
Authors: Elias R. , Wilson M. , Vassilellis G. D. , Bust Vivian
Published: February 2011

This paper discusses a pilot project for exploiting the shallow oil-saturated diatomite located on the Careaga Lease in the Orcutt Oil Field, Santa Barbara County, California. The project is one of two successful new operations underway in the Central Coast of California that show oil production by cyclic steam stimulation of oil-saturated diatomite is possible. This method of oil production has been a success in the San Joaquin Valley since around 1996. It is now extended to a similar accumulation located over 100 miles away.

This case study chronicles the encouraging production response from a similar virtually unexploited zone known for over 100 years. Under full development, expected production could exceed historical peak levels from a resource many considered too shallow and too tight to exploit. Modern techniques are considered vital to making the Orcutt diatomite productive and successful.

The Orcutt oil field is located south of the town of Santa Maria, in Santa Barbara County, California. Discovered in 1901, it was first called the "Santa Maria Field" until the larger Santa Maria Valley oil field was discovered in the mid- 1930's. The name was changed to the Orcutt oil field. Cumulative oil production is in excess of 181 million barrels. Daily oil production is at a 25-year high. It is the largest onshore producing field in Santa Barbara County.
Tight Gas Well-Performance Evaluation With Neural Network Analysis for Hydraulic Propped Fracture Treatment Optimization
Authors: Huckabee Paul , Jin Minquan , Lund Robert , Nasse Dave , Williams Kristin
Published: February 2011

This paper summarizes the application of data mining techniques and neural network multi-variable analysis to evaluate critical parameters impacting well performance and optimize hydraulic fracture treatment design for tight gas well completions in the Pinedale Anticline field in western Wyoming. Challenges and uncertainty associated with single variable analysis are discussed with consideration of the complexity of reservoir parameter variability and nonsequential coincident completion variable modifications. Neural network model development is summarized with emphasis on applications for well performance evaluation and hydraulic fracture treatment optimization. Results are presented from extensive trials performed during 2009 development activity at Pinedale.
Don't Let It Weigh You Down: How To Benefit From Anchoring
Authors: Welsh M. B. , Begg S. H.
Published: February 2011

Anchoring describes the tendency for people's estimates of unknown quantities to be affected by numbers (or information) they have recently seen (or vividly remember). In the oil & gas industry, anchoring is regarded as a potential problem resulting from, for example, the sparsity of data that leads to the common practice of using analogues. "Base Case" or "Reference Case" models can also act as anchors. Much of the anchoring research, however, ignores the question of what estimates look like in the absence of anchoring values. Here we discuss previous research on anchoring and examine the conditions under which anchoring provides a benefit to decision making and whether these occur within the oil industry. We present the results of three studies, the first showing that, while anchoring results in greater deviations from the true value on average, it can also restrict the range of estimates so as to actually reduce the expected error in any single estimate.

The second study follows up on recent research showing benefits from elicitation techniques that cause a decision maker to repeatedly probe their knowledge. Thus, it tests the hypothesis that a decision maker who has seen multiple anchors may produce better estimates. Finally, in study 3, we demonstrate that people with greater knowledge are, in fact, less susceptible to anchors.

We conclude that, while anchoring can cause significant bias in estimates, the judicious use of anchoring values will not necessarily result in worse estimates. Instead, we identify circumstances where providing one or more anchoring values can produce a net benefit in terms of accuracy. Given the use of analogues and "bases cases" within the industry, understanding how anchors affect estimates is essential to improving estimates. This paper demonstrates that anchoring need not always be regarded as a bias to be overcome - rather, sometimes it is a tool that can be used to improve estimates.
Advances in Cased-Hole Compressional and Shear Sonic Acquisition and Processing
Authors: Murray Doug , Endo Takeshi , Sunaga Shin’ichi , Yan Hua Li , Voskamp Arne , Desport Olivier
Published: February 2011

The acquisition of high-quality borehole sonic formation slowness data in cased-hole environments is dependent on cement bond quality. It has generally been considered that when cement bond is poor, cased-hole sonic slowness data quality will also be poor. Additionally, in fast formations, when cement bond is good, casing arrivals can interfere with formation compressional arrivals, and in slow formations the acquisition of high-quality cased-hole dipole shear slowness data can be problematic.

The advent of the latest sonic acquisition technology and related interpretation techniques has reduced these formidable challenges. More powerful sonic transmitters, improved receivers, altered transmitter-receiver spacings, and fundamental changes in tool design have meaningfully improved the acoustic signal-to-noise ratio. An improved understanding of cased-hole borehole acoustic modes, the ability to transmit acoustic energies at more optimal frequencies, and the capability to simultaneously acquire cement bond log information have all contributed to improved cased-hole sonic slowness logs.

With the latest technology, accurate formation compressional slownesses can now be extracted in previously problematic cased-hole environments that contained either poor cement bond or fast formation slownesses near to the casing arrival. Additionally, dramatic improvements are evident in formation shear slowness acquisition in very slow formations where previous cased-hole technology had been unsuccessful.

These developments have a profound impact on drilling operations, seismic velocity modeling, geomechanics, and reservoir characterization. In existing cased wells, the latest sonic technology presents a viable option to acquire critical compressional and shear slowness information. In newly drilled wells, the feasibility of acquiring accurate cased-hole slowness information can reduce the necessity and the inherent risk of an openhole logging run.
The Maturity of Organic-Rich Shales Using Microimpedance Analysis
Authors: Kenechukwu C. , Prasad Manika , Batzle Michael L.
Published: February 2011

The increasing importance of organic-rich shales, ORS as hydrocarbon reservoir rocks has lead to a demand for better understanding of the processes that lead to shale maturity. An improved understanding of these processes in the laboratory can lead to development of methods for their indirect geophysical detection at in-situ conditions. Present day methods for maturity detection by geochemical means is limited by spatial density of sampled wells and sample availability. The study of maturity relationships with rock physical properties and microstructure can lead to methods for indirect detection by establishing correlations between rock character, kerogen content and maturity. This would allow for improved project economics in exploration and development of shale oil fields.

In this paper we show how micro-impedance can be used to understand textural and anisotropic relationships with maturity. Microscale anisotropy increases with kerogen content, a measure of organic matter. This observation is supported by published reports of studies made at the core (centimeter) scale. Mineralogy also contributes to anisotropy; clay-rich shales have higher anisotropy, while silica-rich shales appear more isotropic. The Young's modulus of kerogen is shown to increase linearly as kerogen matures. Our findings could serve as considerations for improving petrophysical models aimed at indirect and in-situ detection of maturity.
Sea Water Injection Mobile System (SWIMS) for Waterflooding Marginal Offshore Oil Reservoirs: A Case Study From Tantawan Field, Gulf of Thailand
Authors: Rexilius J. P. , Sahni A.
Published: February 2011

Seawater Injection Mobile System (SWIMS) is a novel concept involving the use of portable equipment (high pressure pumps, tanks, filters and hoses) to take seawater from the ocean, treat it with anti-corrosion and anti-bacteria chemicals, pump it at high pressure's into a well at surface, and subsequently waterflood subsurface oil reservoirs.

SWIMS is designed to unlock significant waterflood reserves distributed over small reservoirs across several offshore platforms in an oil field. The system is modular, flexible and mobile; attributes that help get water in the ground quickly and cheaply, resulting in incremental waterflood reserves from marginal offshore oil reservoirs.

The concept works best in small, high permeability, homogenous reservoirs and in a favorable mobility ratio environment. In such a scenario, water can be injected at rates significantly higher than off-take rates while still maintaining stable displacement. This allows for quick waterflood processing of small reservoirs and SWIMS can be de-mobilized and rigged up on another platform to repeat injection.

The SWIMS system allows implementation of waterflood projects on platforms which do not warrant the laying of a produced water pipeline and installation of injection facilities offshore. This low cost and flexible system thus enables recovery from small offshore oil reservoirs that would usually not be subjected to waterflooding due to economic constraints.

The SWIMS concept was trialed on an offshore platform in Tantawan Field, Gulf of Thailand (GoT) in January 2010. Post-drill subsurface characterization studies revealed a waterflood opportunity in a small oil reservoir penetrated by 3 wells. Best practice geological correlating, RFT pressure data collection and interpretation, and a successful interference/pulse test were used to confirm reservoir connectivity prior to execution of the marginal waterflood. Waterflood response was observed soon after start-up of injection, with a pronounced increase in oil rate and pressure, together with a reduction in gas-oil ratio at a voidage replacement ratio of between 1.5-2.

This paper will outline the details of SWIMS including the equipment utilized, fit-for-purpose chemical treatment and corrosion monitoring programs, as well as other key attributes of the unique system. The subsurface characterization work leading to the identification of the pilot waterflood in Tantanwan field will also be discussed along with production results and waterflood evaluation of this successful application of SWIMS in the Gulf of Thailand.
Next Generation Multi-Stage Completion Technology and Risk Sharing Accelerates Development of the Bakken Play
Authors: Houston Matt , McCallister Mark , Jany Josh , Audet Josh
Published: February 2011

Over the last decade, an industry wide shift to unconventional plays has occurred due to advanced drilling and completion technologies allowing the recovery of previously uneconomic reserves. A notable play in this category is the Bakken formation in the Williston Basin. Through the application of horizontal drilling and innovative completion design, the recoverable reserves in the Bakken are now estimated at 3.65 billion bbl of oil.

Through multiple case study wells and direct offset comparisons, this paper analyzes production results for two completion methods employed in the Bakken today: cemented production liners with "plug and perf" stimulation and open hole, multi-stage system completions. Additionally, production differences based on stage number, stage interval length, and 640 acre spacing versus 1,280 acre well spacing are presented.

The trend to increase stage density in extended-reach, horizontal wells in the Bakken requires leading-edge technology to maintain operational efficiencies and improve overall well economics. With the introduction of new "high density" technology to open hole, multi-stage systems, these requirements are exceeded with maximum stage density capability allowing for decreased completion time and lower-risk stimulation practices compared to conventional methods.
Capacity and Constraints for Carbon Dioxide Sequestration in Aquifers and Depleted Oil/Gas Reservoirs in Carbonate Environment
Authors: Gupta Anuj
Published: February 2011

Production of oil/gas to meet the increasing energy needs results in generation of significant amount of CO2. This study presents results of experimental and simulation work to understand opportunities and challenges in sequestering CO2 in carbonate rocks typical of aquifers and oil/gas reservoirs in the Middle East. CO2 corefloods were conducted in samples from carbonate analog outcrops to simulate sequestration process, and, changes in the pore-space due to dissolution/precipitation were quantified by time lapse CTscans and measurement of relative permeabilities. Density and compressibility of CO2 and Solubility in reservoir brines was measured to calibrate predictive models and used in simulation studies.

Objective is to reliably calculate sequestration capacity available in aquifers and depleted reservoir in a region, and to evaluate the long-term stability of seals in such systems. Experimental results facilitate reliable simulation studies which are very important for determining how much CO2 can be sequestrated. Such studies also lead to understanding of potential leaks due to interaction of CO2 with carbonate minerals of sealing formations.

Density and compressibility measurements of CO2 are reported at up to 5000 psia and 250 F. The results show good agreements with available predictive models and were used to calibrate parameters in such models. CT-scans and petrophysical properties of core samples show dissolution in some pores but precipitation in other pores of carbonate matrix. Simulation study reports ranges for storage capacity in tones/acreft.

The results of this study are directly applicable for evaluating CO2 sequestration opportunities in Qatar, Middle-East since the outcrop samples studied are analog for Arab and Khuff Formations, which hold most of the petroleum reserves in the Middle-East. CO2 properties and its interaction with carbonate matrix are significant for CO2 sequestration study anywhere.
Effect of Dispersant on Asphaltene Suspension Dynamics: Aggregation and Sedimentation
Authors: Hashmi Sara M. , Firoozabadi Abbas
Published: February 2011

When oil is mixed with light alkanes, asphaltenes can precipitate out of oil solutions in a multistep process that involves the formation of nano- and colloidal scale particles, the aggregation of asphaltene colloids, and their eventual sedimentation. Amphiphilic dispersants can greatly affect this process. The mechanism of the dispersant action in colloidal asphaltene suspensions in heptane has been shown through previous work to be due in part to a reduction in the size of the colloidal asphaltene particles with the addition of dispersant. However, previous studies of the sedimentation behavior have also revealed evidence of aggregation processes in the colloidal asphaltenes in heptane that has yet to be investigated fully. We investigate the effect of dispersants on this aggregation behavior through the use of dynamic light scattering, showing that both the amount of dispersant as well as the amount of heptane dilution can affect the onset and extent of aggregation in colloidal asphaltene suspensions. The light scattering results match well with those obtained through the macroscopic sedimentation experiments.
Continuous Wellbore Surveying While Drilling Utilizing MEMS Gyroscopes Based on Kalman Filtering
Authors: ElGizawy Mahmoud , Noureldin Aboelmagd , El-Sheimy Naser
Published: February 2011

The current method to compute the wellbore while drilling is based on stationary surveys at the desired station. This is done by measuring the inclination and the azimuth of the borehole between the current and the previously surveyed stations. Using a mathematical model based on assumptions of the shape of the drilled section, the coordinates of the borehole can be derived. This current method neglects the actual trajectory between the two surveying stations.

Exploration and production companies demand cost effective drilling operations. Thus, demand has been rising for a continuous survey that captures the actual trajectory between the stationary surveying stations. This provides an actual estimate of the curvature "dogleg" along the well trajectory. In addition, this allows a better estimation of the casing and cementing of the borehole. Therefore, in this development the wellbore trajectory between the two surveying stations is continuously surveyed using three accelerometers and three MEMS gyroscopes. The computation algorithm is based on strap down Inertial Navigation System mechanization and Kalman filtering.

The inputs to the continuous drilling survey system are the accelerometers and gyroscopes measurements, while the outputs are position, tool face, inclination and azimuth of the drill bit. This wellbore survey system will exhibit an unlimited growth of position, and azimuth errors if there are no external observations to update the surveying system. Two external update schemes can limit this error growth while drilling. The first is based on the continuous source of drilled pipe length measurements while the second is the zero velocity update. The Kalman filter continuous surveying system was successfully applied to drilling tests. External updates of the drill pipe length were utilized to reduce measurement error drift. When the drilling process was stopped to connect new drill pipe stands, zero velocity updates were employed by the Kalman filter.
Numerical Model for Interpretation of Distributed Temperature Sensor Data During Hydraulic Fracturing
Authors: Seth Gaurav , Reynolds Albert C. , Mahadevan Jagan
Published: February 2011

Injection of cold fluids into tight gas formation during hydraulic fracturing results in cooling of the formation around the fracture and the wellbore. Fluid leakoff from the fracture causes a non-uniform temperature distribution around the fractured zone. Subsequently, during the shut-in period, the near fracture region warms up due to heat flux from the external reservoir rock. Thus, the near wellbore region is subjected to cooling and then warm back which can be measured by the use of distributed temperature sensors (DTS). In this study we develop a numerical model to calculate the temperature during both hydraulic fracturing and the shut in period.

The numerical model solutions can be used to interpret field data from the DTS during hydraulic fracturing, to estimate the fracture length, and when coupled with a wellbore model, to quantify the total volume of fracturing fluid injected into an interval. Additionally, the model developed can be used in a temperature history matching algorithm to obtain characteristics of the hydraulic fracture. The models are validated using analytical limiting case solutions.
Global Application of Coiled-Tubing Acid Tunneling Yields Effective Carbonate Stimulation
Authors: Stanley F. O. , Portman L. N. , Diaz J. D. , Leonard Darmawan R. , Strasburg J. P. , Clark J. S. , Navarro M. S.
Published: February 2011

Since 2005, a stimulation technique termed "coiled tubing acid tunneling" has been successfully applied on limestone and dolomite reservoirs in several regions around the world (South East Asia, USA, South America, Europe and Middle East). The technique is applicable on carbonate wells with barefoot (open hole) completions, with either relatively thick pay zones, or with thinner pay sections, for example with close water contacts. It consists of creating multiple drainage holes (tunnels) out into the reservoir pay zone. The tunnels are created by pumping hydrochloric acid (HCl) through a specially designed jetting bottom assembly (which includes a special kick off tool and procedure) and uses conventional coiled tubing and acid pumping equipment. Typical acid tunneling is performed on complete losses, resulting in a negative skin completion. The purpose of these drainage holes (with its own network of worm holes) is to improve the connectivity between the reservoir and the wellbore and positively impact well production.

The process can create as many drainage holes as required at different depths (production simulators are used to estimate optimum number of tunnels). The depth selections are based on key well information such as available logs (image, resistivity, caliper, drilling), past reservoir knowledge of the zone and observed lost circulation zones while drilling.

Results of this new stimulation technique on carbonate wells have been excellent as compared against conventional acid work (matrix acidizing, conventional acid jetting with coiled tubing and acid fracing). Numerous case histories from each region of the world are included in this paper and will contain comparisons of acid tunneling to conventional stimulation methods, stimulation design criteria, operational procedures, and production results. In one specific Indonesia field the pretotal average production on 12 wells was 955 bopd while the post acid tunneling result was 1,670 bopd, sustained production (the early 5 wells now have between 850 to 950 days post tunneling production history and all wells have at least 300 days post tunneling history).
A New Look at Nonlinear Regression in Well Test Interpretation
Authors: Dastan Aysegul , Horne Roland N.
Published: February 2011

Nonlinear regression is a standard procedure in the oil industry; however, its practical applications can be constrained by issues observed commonly in real data sets. These issues include convergence performance that depends on starting guess, deviations in the time and pressure data, nonideality in the data, and ambiguity in parameter estimation – these issues limit the ability of well testing results to forecast future reservoir performance. We investigated a variety of strategies to improve nonlinear regression and reduce the susceptibility to these issues.

The first strategy we investigated is Cartesian transformation of the parameter space. We developed transform pairs for common reservoir parameters and achieved performance improvement in terms of higher probability of convergence and smaller number of iterations for a random starting guess. In the second strategy, we applied the wavelet transform to the pressure data. We conducted nonlinear regression on a reduced wavelet basis to achieve improved likelihood of convergence and narrower confidence intervals. Wavelet analysis provided robust interpretation of dual-porosity reservoirs and reservoirs with boundary effects. In the third strategy we used total least squares for accurate estimation of reservoir parameters in the presence of deviations in the time data as well as deviations in the pressure data. We developed a robust approximation for total least squares (orthogonal distance regression) for the nonlinear pressure transient function.

We tested the techniques rigorously by using a large matrix of test cases made up of real and generated well test data sets. The data sets include a selection of reservoir models and test scenarios, including dual-porosity and fractured reservoirs, reservoirs with rectangular boundaries, cyclic buildup-drawdown tests, and general multirate data. We determined the methods or combinations of methods that work best with a particular reservoir model or type of test. We have shown that these novel nonlinear regression algorithms greatly reduce the ambiguity (narrower confidence intervals) and provide robust parameter estimation even for large noise levels or data uncertainty. We demonstrated that our techniques provide faster convergence and are more robust to poor initial guesses. The techniques provide compression and automatic denoising of massive data sets from permanent downhole gauges. We expect that our techniques and analyses will allow for better forecasting of reservoir performance.
Role of Vapor Phase in Oxidation/Combustion Kinetics of High-Pressure Air Injection (HPAI)
Authors: Barzin Y. , Moore R. G. , Mehta S. A. , Mallory D. G. , Ursenbach M. G. , Tabasinejad F.
Published: February 2011

Oxidation reactions and their kinetics are acknowledged to have a major impact on the success of air injection-based improved recovery processes. Vaporization of oil has been reported in the literature as a mechanism associated with kinetics of air injection processes; however, the parameters which control the vapor phase oxidation/combustion behavior have not been included in the studies of oxidation kinetics.

In order to characterize the vapor phase oxidation/combustion behavior of light oils in high pressure air injection (HPAI) process, an experimental and a follow up numerical study have been conducted on a high pressure ramped temperature oxidation (HPRTO) reactor on a 37 ° crude oil and a pure hydrocarbon.

The results of this study indicate that phase equilibrium between the liquid and vapor hydrocarbon and water components has a definite impact on the "flammability range" for vapor phase combustion at given temperature and pressure conditions. The observations also suggest the potential participation of vapor phase oxygen addition reactions in the supply of triggering energy for spontaneous ignition.

Given the importance of vapor phase behavior on the amount and distribution of hydrocarbons available for reaction with oxygen, a comprehensive phase behavior study on the selected light oil was performed. The developed phase behavior model was then used in a hypothetical model to study the behavior of the vapor phase under conditions of HPRTO tests. The significance of this model is its capability to predict the theoretical injected-air/fuel ratio of the vapor phase assuming thermodynamic equilibrium.
First Application of Alternate Path Technology and Concentric Sandface Completion Improved Operational Efficiency and Saved Significant Rig Time
Authors: Saebi Shahryar , Tyutikov Sergey , Bahri Chahine , Elhusseiny Moustafa , Bela Sunanda Magna , Ibrahim Zahidi
Published: February 2011

In line with the production enhancement program in Malaysia, Petronas Carigali Sdn. Bhd. (PCSB) decided to workover a number of idle wells in an offshore field. The reservoir consists of highly unconsolidated, laminated sandstone formation that requires having solid sand control system in place prior commencing production. There were concerns about the possibility of heavy losses of completion fluids in the depleted reservoir and also complications in gravel packing lower zones by presence of existing perforations in the upper zones. The operator also demanded to have selective production capability from the various zones during the life of the well.

In order to address the challenging requirements of the project, a combination of two completion techniques were proposed. Alternate Path technology provides alternate slurry pathways that bypass the bridges to assure 100% packing efficiency. Concentric Completion system provides fluid loss control post gravel placement and also circulation flow path during gravel placement and selectivity during production.

The customized sand control system was successfully installed, achieving the operational objectives.
Increasing the Reach and Selectivity of Completions in Extended Reach Horizontal Wells
Authors: Ritchie Barry , Pitts Michael , Van De Ven Sebastianus , Abul-hamd Abdel Aziz Ibrahim
Published: February 2011

Over 15 years of production and injection history within the Al Shaheen Field has provided more details on the reservoir heterogeneities and performance of extended reach horizontal wells. This additional data, along with the lateral extent of the reservoirs, has increased the need for longer and more selective horizontal completions. Three primary reservoirs have been developed to date and have different requirements regarding liners and completions. The commonality of all reservoirs is the requirement for long liners and completions in vertically shallow horizontal wells.

As the completion philosophy has changed, new approaches have been developed for both deployment and selective isolation. A number of case histories are discussed to illustrate the evolution of the completion requirements. Modifications to zonal isolation, mud over air floatation, and remote triggered packers are some of the cases discussed.

Two of the three reservoirs require acid stimulation to improve the production and injection performance of producers and injectors. Effective stimulation can not be accomplished through what would be considered typical placement techniques, due to the extreme lateral departure of these wells in shallow vertical reservoirs. Two techniques used are described along with some issues regarding hole-geometry in acid stimulated wellbores.

The paper concludes with some future requirements for the further development of the Al Shaheen Field. Increased selectivity and the need for active zonal control will push the completion requirements beyond where they are today. New completion concepts are being actively researched and developed so that the reservoirs can be optimally managed.
Design and Evaluation of Perforation Performance Using Dynamic Under Balance – North Sea Case Histories
Authors: Tovar J. , Appleby R. , Cooper G. , Hamilton B.
Published: February 2011

Dynamic under balance (DUB) pressure is being used by operators to improve completion efficiency and minimize formation damage. An understanding of the pressures generated when perforating allows the prediction of the level of pressure differential required to overcome the surge pressure generated, leaving a clean connection between the wellbore and the reservoir. Results reported by different operators indicate success with the DUB technique; certain criteria have been developed for the determination of the optimum conditions for its use. From the published information, type of reservoir fluid, interval length and formation mechanical properties are some of the main considerations for a successful design and implementation of the technique. Talisman Energy UK has used DUB for perforating several wells in the North Sea. A detailed job design process was implemented starting with the need to characterize the level of formation damage that existed in the wells. Three (3) main damaging mechanisms were quantified; damage resulting from fluid and solids invasion into the reservoir matrix, mechanical damage generated during drilling operations and actual damage caused during the perforation process. Perforation programs were developed and executed based on a clear understanding of the rock mechanical response to the DUB generated by the gun and taking into consideration perforating debris and fluid inflow required to clean the tunnels. The results from this work indicate that current design criterion for the selection of the optimum DUB pressure is limited and it is not clear about the physics and hydrodynamics of the clean up process.
Developing an Invisible Field in the North Sea
Authors: Berntsen B. A. , Hagen E. , Sørlie R. , Gowers M. , Jones C.
Published: February 2011

What can you do with a small oil discovery where you cannot map the reservoir on the seismic data? With a big field the answer is simple: drill more appraisal wells. But in a small offshore field with marginal economics this approach will be uneconomic. The Hanz field in the Southern Viking Graben of the Norwegian North Sea is such a discovery. It is small relative to North Sea oil fields and the seismic data does not allow direct mapping of the reservoir geometry. The discovery consists of two thin sands, an upper gas-filled sand and a lower oil-filled sand. The uncertainty concerning the relative amounts of oil and gas makes development planning difficult. The geology of the reservoirs indicates a coastal shoreface environment and a nearby well shows that the sands are only locally developed, adding another major uncertainty to the reserves.

However this discovery is unusual in one respect: a full scale DST was conducted in the lower oil sand and proved excellent permeability. A multidisciplinary subsurface team took up this challenge and embarked on a project to use the DST data to investigate the geometry of the trap. Normally an engineer's estimation of boundaries and volumes from a DST takes the form of a rectangular box-like reservoir with specific distances to boundaries. In the case of Hanz, the stratigraphic information from the surrounding geology was used to build a series of reservoir models. These models were used to simulate the DST results. In an iterative process the results of the DST simulation were used to adjust the model and simulate a new case. This work process turned out to be very efficient with a turnaround of two days from start of a new model to DST simulated results. This again enabled modeling of a large range of possible geometries, and the subsequent exclusion of a good many alternatives. This enabled the range of uncertainties for the discovery to be significantly reduced, and a workable development plan constructed. The Hanz discovery would never be developed without the available DST. The discovery is simply too small to justify an appraisal well. The next well on Hanz will have to be a combined producer and appraisal well. Based on this work, a robust subsurface foundation has been established for a future subsea standalone development or a third party tie-in candidate in a mature area with good infrastructure. The paper also illustrates the criticality of being able to perform a full scale DST well test in the first exploration well on a prospect in a mature but high cost offshore environment and where all the large structures and fields have been drilled.
Installation of a Produced Water Treatment System on Raml Field (Western Desert), Egypt
Authors: Surace D. , Broccia P. , Salemi Y. , Lovane M.
Published: February 2011

During hydrocarbons extraction from reservoir a big amount of water is produced. The volume of water does not remain constant over time, but the percentage increase passing the time. The presence of water enlarges the hydrocarbons production costs since it decrease the productivity capacity of the wells, increasing the treatments complexity of hydrocarbons. The water treatment is a delicate issue in the oil industry, both from economical and environmental point of view.

In the last years eni has developed different R&D projects for optimizing the water treatment processes and for improving the quality of the water. The produced water, once treated, can be reinjected into the reservoir or discharged in surface (sea, rivers, desert). The use of innovative technologies both onshore and offshore has allowed the discharge of water into surface bodies with oil in water concentration less than country regulations where the reservoir is placed.

This paper presents an ongoing project concerning the application of a produced water treatment system in the Raml field (Western Desert) in order to improve quality of the produced water, reaching the required target for the reinjection (oil-in-water ≤10 ppm and total suspended solids ≤ 15 ppm) also minimizing operations management and equipments maintenance.

A testing campaign on the deoling system, part of the water treatment system, was done on January 2010. This paper reports the processand scheme developed and the positive results obtained during this trial.
Difference Between Traditional and Risk Based Auditing
Authors: Spadaccini Danny
Published: February 2011

Auditors are trained to make detailed examinations of the internal control systems such as ISO 9001, ISO 29001, ISO 14001, OSHAS 18001, API, accounting systems and various legislative requirements and; focus their audit planning, testing, and reporting on internal controls in the business process.

The Evaluation of controls without first examining the purpose of the business process and its risks provides no context for the results. How can the internal auditor know which control systems are most important, which are out of proportion to their risk, and which are missing?

When controls are the central theme of the internal audit, audit reports and recommendations are generated for improving and strengthening internal controls. Over time, layer upon layer of controls are built up. These excessive layers of control slow down business processes, communication becomes more difficult, and people are employed in non-value-added work.

Auditors are typically looking at control activities designed at some previous time to deal with issues that were relevant when systems were implemented. This means the internal auditor is examining activities that may or may not be relevant to current risks. The controls may be inappropriate because they monitor risks that are no longer important or even in existence.

RBA changes the way internal auditors think and talk about risk. Instead of focusing on history, audit reports address the present and the organization's level of preparedness to deal with the future. Internal audit reports "complete the loop" between assurance of control in current operational plans and input to risk assessment for the strategic plan. RBA places an emphasis on risk-based internal audit reports rather than on traditional controls-based reports.
Three Dimensional FEM Simulation and Parameter Study on Laden Torque of Interference Friction of PCP
Authors: He Liu , He X. D. , Wu H. A. , Wang X. X. , Cao G..
Published: February 2011

A three-dimensional finite element model for Progressive Cavity Pump (PCP) is constructed. The steel stator is simplified as a rigid body and the deformation of the rubber rotor is considered in the model according to the characteristic of the stator and rotor materials. The laden torque of friction due to the interference between stator and rotor is calculated with the model. The obtained numerical results are consistent well with experimental data. The effect of parameters on laden torque is performed and discussed. The parameters include the amount of interference between stator and rotor, eccentricity of the track of the rotor moving etc. The results demonstrate that the amount of interference between stator and rotor is the major factor of influencing the laden torque and the laden torque reduces as eccentricity decrease.
Gas Content Measurement With and Without the Use of Coring
Authors: Gray Ian
Published: February 2011

This paper examines alternatives to using core for gas content measurement of coal. The measurement of gas content from cuttings is presented in two forms, one involving the recovery of cuttings with air drilling and the second involving the collection of all released gas from the hole during overbalanced drilling. The latter approach is suitable for not only coal but all gas bearing formations such as shales which do not have major open pore space such as vugs.

Core desorption is the standard process for determining the gas content of cores. This process is described by McCulloch and Diamond (1976), and more recently Standards Australia (1999). The process generally involves using wireline coring to cut a core so that the core may be retrieved quickly. Once the core is retrieved to surface the core is placed in a canister and the released gas is monitored with respect to time. This should be undertaken at reservoir temperature. An example of gas release versus time is shown in Fig. 1.

Once the core has been further desorbed the canister is opened and the core is logged and weighed with density determination. Weighed sub sections of the core are then crushed to enable the remaining gas to diffuse out more quickly than from the core.

This process is relatively straight forward but the determination of the gas lost before the core is placed in the canister is not. The usual process adopted is to assume a time when the core begins to release gas and to plot the gas release with respect to the square root of time. An example of such a plot is shown in Fig. 2.