bluuebunny/crossref_metadata_2025 huggingface dataset:
m-Health Solution for Keeping Employees Informed
Authors: Nicosia V. , Mika F. , de Sanctis S. , Alfano G. , Gialdi C. , Consentino M.
Published: June 2014

Saipem, with more than 46,000 employees, is one of the biggest contractor company in oil and gas industry. Operation’s in Oil and Gas industry require movements of a great number of persons from one part of the world to the other and the operations are more and more being routinely carried out in remote and extremely remote locations in countries and areas that re unknown to the employees. Regardless the remoteness of the operations or the difficulties in the country of assignment it is company’s obligation and duty of care to assure not only the best possible medical assistance to the employees working in such extreme environments but also the information and training of the employees assigned. A part the work related ones, the workplace risks vary from infectious diseases to climate, environmental and psychosocial factors. In order to assure the proper preparedness and full information about the working location of the personnel assigned for expatriation Saipem’s Occupational Health Dept. developed a pre travel counselling program. As work related risks are discussed elsewhere this counselling is mainly for the prevention of infectious and other risks, both general and specific, related to expatriation.

Following the WHO (World Health Organization – Bejing declaration) on "Global Strategy on Occupational Health for All" (1994), as well as the European Legislation and 2000/54/EC on protection of workers from risks related from exposure to biological agents at work, and its application in Italy by a Legislative Decree n. 81/2008 and its modifications (called "Testo Unico" for Health and Safety in Workplace L.D. 81/08) Saipem S.p.A. has developed this program for all the employees –Pre-employment accurate medical examination is performed to assess the worker’s fitness against the risks related to geographical area and occupational activities to prevent illness and/or injury. (Art. 41 L.D. 81/08 Health Surveillance)–Before departure the worker is informed through a counselling program about local risks and gets the protective means (vaccination, prophylaxis, repellents etc.) he/she will need. (Title X on Biological Risk, articles 278–279 about L.D. 81/08 )–Health surveillance program is implemented during the assignment of work.–End employment medical examination assess the worker’s fitness.–Health promotion program include training and information about lifestyle, company’s policies, health promotion activities (Art. 25 L.D. 81/08)

To assure the fulfilment of training program and legal requirement, apart the counselling done face to face a hand pocket Manual of Travel Medicine (Si Viaggiare) is provide to all Saipem’s employees when they start to work for the company. The objectives is to supply all Medical information related to Travel Medicine. The Manual is anyway part of our Counselling Program (art. 278–279).
Safe Work Practices and Rescue Planning for Vertical Column Work during Turnaround: A Case Study
Authors: Daher Elie , Case George , Davis Gordon , Dowd Darrell
Published: June 2014

Managing long term turnaround programs to carry out maintenance on offshore facilities can be rewarding for safety system companies and its customers because it maximizes efficiencies in the delivery of services by allowing continuity of learning and improvement.

A 60-day turnaround for an offshore facility gave a safety company and its customer in Angola the opportunity to improve processes and skills in emergency rescue operations. One of the work activities involved opening, cleaning, inspection and repair of a vertical Deethanizer Column that is over 60 feet high and only three (3) feet in diameter. At the top of each of three packed sections of the column is an 18" diameter man-way. This man-way is the only entry and exit point on the column which sits on the corner of the offshore platform, 52 feet above sea level.

For the safety provider, a major concern was how to rescue a crew member from inside the column, if injured or incapacitated considering the vertical column’s narrow diameter. The team needed a safe rescue procedure prior to the turnaround. With support from the Facility Engineers, a mock-up structure was designed to simulate one ring section of the column, using a section of 36" pipe with 18" man-ways.

This mock-up provided many benefits including the opportunity to install one of the trays as would be performed in the field, the familiarity with the installation procedures by allowing trial runs, and pre-fitting trays in the mock-up that ensured parts fitted and the dimensions were correct. Most importantly, it gave the rescue crews a chance to practice a rescue operation on the offshore platform.

This paper takes a detailed look at the best practices, lessons learned and steps undertaken to develop safe work practices and rescue operations during a turnaround in an offshore facility in Angola.
Assessing and Selecting Remote Sensing Techniques for Early Detection of Oil Spills
Authors: Grimsrud Torleiv Stien , Nissen-Lie Torild , Vandenbussche Valentin
Published: June 2014

While many parameters influence the environmental consequences of oil spills, the quantity of oil released remain one of the most important. The total volume may be expressed as the leak rate multiplied with the duration of the discharge. By detecting a spill at an early stage, it could be possible limit the duration and hence the amount spilled. Early detection can also instigate a rapid response, which is another crucial consequence reducing measure.

Detection technologies are becoming increasingly important as the petroleum industry is progressing into Arctic areas and closer to shore or environmentally sensitive areas. With increased environmental concerns and stakeholder engagement, company integrity and accountability are essential for maintaining a license to operate.

The requirement for leak detection capabilities for oil and gas activity varies. At the Norwegian Continental Shelf, operators are required to detect pollution of significance within a short time, usually between one and three hours. Leak detection systems must also be effective regardless of darkness, sight and weather conditions. On behalf of the Norwegian Oil and Gas Association, a methodology was developed for assessing and selecting remote measurement techniques for specific fields.

For the leak detection system to be effective and reliable, it is vital to select appropriate techniques that complete and complement each other. The methodology firstly maps relevant requirements, risks, facility limitations and field specific factors. A BAT (best available techniques) framework is used to identify appropriate technologies, while gap analyses may map the overall limitations and flaws by comparing a proposed system’s performance with the requirements. Gaps and/or weaknesses are further evaluated through an ALARP (as low as reasonably practicable) analysis assessing the cost and benefits of additional techniques. The methodology provides the operators with valuable information concerning factors affecting the performance. Finally, organizational measures are crucial for ensuring effective operations and it is necessary to integrate leak detection into facility management systems.

This paper presents the complete methodology and explains how a structured approach can be applied to both existing and new installations. It provides examples of how assessments are conducted and an overview of the most relevant remote sensing techniques. The methodology has been reviewed by several operators and been employed for numerous projects. While the framework was developed for the Norwegian sector, it is relevant and applicable for installations globally.
The Value of Periodic Fitness for Work Evaluations in Disease Prevention, Disease Burden Reduction and Promotion of Public Health Initiatives among the Local Workforce of an Offshore Drilling Company an a Developing Country: A Case Study
Authors: Awotula Patrick Oluwole , Pelat Francois
Published: June 2014

Fitness for work evaluations though, the subject of much debate in the medical community find particular relevance in the oil and gas industry. The peculiar and demanding nature of this industry imposes restrictions on medical conditions that may pose a threat to the safety of individuals and their colleagues at work; consequently the primary purpose of medical evaluations in this context is to determine fitness to perform the tasks at work in a safe and effective manner without risks to the health and safety of the employee and others.

There is a significant overlap in fitness for work assessments and health screening. Some of the processes involved in general health screening are inherent in the medical assessment for fitness to work. This potential can be profitably utilized in the delivery of simple but effective health initiatives at little or no extra cost; this can enhance long term prevention of ill-health and maintenance of fitness to work. There is significant added value to the employer in terms of possible reduction in sickness absence and increased worker efficiency.

The process of the examinations, the ancillary investigations, assessment of risk factors, and the actual consultations provide a unique opportunity to review the health impact of lifestyle choices and promote healthy behaviors. In developing, infectious diseases are a significant cause of increased morbidity and mortality. Many of these conditions are both preventable and treatable; awareness to this can be significantly enhanced by capitalizing on the opportunity provided by the fitness evaluations to educate employees and disseminate awareness materials.

This paper intends to demonstrate how fitness for work evaluations can be optimized to meet the challenges of implementing work place health initiatives, health education and promotion. It will also cover the delivery of low-cost but effective primary public health interventions that have the potential to impact employees, their families and by extension the larger community.
Do You See What I See? Viewing Safety from the Lens of a Contractor
Authors: Brown Michelle , Krauss Autumn D.
Published: June 2014

In the oil and gas industry, contractors serve critical roles during construction, production, and maintenance. With how imperative contractors are for effective operations, it might be assumed that they are enabled to flawlessly accepted and integrate into not only the company’s practices, but also its culture. Unfortunately, research has shown that this is often not the case, with an "us vs. them" mentality existing even for long-standing contractors.

One area where differing views may be particularly prevalent is workplace safety. While some historical stereotypes, such as bringing in contractors to do the particularly dangerous work or not providing them with sufficient personal protective equipment, may now be outdated, it is possible that contractors and permanent employees continue to have different perceptions about safety onsite. These differences could hinder the ultimate goal of a strong cohesive safety culture, so they are important to measure and understand. With this objective, perceptions of organizational and team safety climate dimensions along with safety performance metrics were gathered from contractors and permanent employees working across industries, including the oil and gas sector.

Research findings included the following: After controlling for company, age, tenure in industry, and tenure with current employer, contractors were 33% more likely to be involved in a safety incident than permanent employees.Contractors possessed significantly more favorable perceptions of organizational safety climate, with the largest differences being observed for perceptions of on-boarding and safety training quality.Contractors possessed significantly less favorable perceptions of work-safety tension and supervisor production pressure.

Overall, the findings from the study show the complexity of contractor safety; it is not overall worse or better than permanent employees. The paper and associated presentation will offer further explanation and interpretation of the sample results above as well as additional results from the study.

This study highlights the intricate nuances of the psychological aspect of contractor safety management. With the goal being a strong positive safety culture onsite, the alignment between contractors and permanent employees is critical. Through this type of research, the oil and gas industry can identify the largest areas of misalignment, those that significantly predict safety performance, and target these for intervention and improvement.
Hydraulic Fracturing: Tools for Successful Engagement With Fence-Line Communities
Authors: Kinslow Carla J.
Published: June 2014

Being frightened of the unknown is a natural and essential human response. Most people in the US have never seen a hydraulic fracturing facility and know relatively little about their operations, and yet many have already developed opinions about their safety and environmental impact based on reports in the media. Energy companies must recognize and prepare for this reality when approaching communities where the development of hydraulic fracturing facilities is now being proposed.

Dr. Kinslow presents several examples of community engagement strategies as they relate to the energy industry, specifically hydraulic fracturing, in Texas and other states. Through these examples, she illustrates how applying the three tools of commitment, transparency and dedicating the right people for this type of engagement are critical to addressing community concerns and to the economic success of hydraulic fracturing.

Commitment to the community involves a proactive response to questions and concerns of the community. Interestingly, many concerns from fracking communities do not coincide with those concerns illustrated in the media. Proactively recognizing and addressing these issues learned from past experiences places the industry in a solid position to build a trusting relationship. Transparency is essential in this relationship. The Texas Commission on Environmental Quality (TCEQ) has developed an outstanding and transparent system of engagement, datasharing and strong community outreach. This Agency-wide attitude has gained the TCEQ standing as a science based, strategic, and trust worthy group to turn to when human health impacts are an issue in state and federal regulatory decision making. Having the right people to bring these tools forward is essential for successful engagement. This team must involve a set of communicators that are ready to apply their scientific, business, and regulatory knowledge in order to help people in the communities understand the safety and environmental issues. Communities know when someone is not genuine. Having the right people at the front lines to build and maintain that genuine relationship through knowledge sharing will gain respect and trust on all sides.
The Use of a Weight-of-Evidence Approach in Assessing the Ecological Effects of Produced Water Discharge Offshore Nigeria
Authors: Richardson N. A. , Tilstone A. M.
Published: June 2014

A weight-of-evidence (WOE) approach was used to evaluate whether produced water (PW) discharges in the Gulf of Guinea, offshore Nigeria were having an undesirable effect on the marine ecosystem. The Nigeria study comprised an evaluation of PW constituent fate and effects in biotic (tissue) and abiotic media (receiving water and sediment), and laboratory bioassays of PW effluent. Lines of evidence (LOE) included: 1) laboratory toxicity testing, 2) assessment of chemical constituent spatial and temporal trends, 3) background comparisons and 4) toxicological benchmark comparisons. The LOE were evaluated based on data quality, consistency, degree of severity, and relevancy, and then integrated to arrive at an overall conclusion. The WOE approach concluded that potential incremental ecological risks associated with the discharge of PW constituents were inconsequential and no unacceptable risks were predicted to occur beyond the prescribed mixing zone boundaries. The study demonstrated the value of the WOE approach in evaluating potential environmental effects such as those associated with oil and gas development and operations.
Health Impact Assessment For Global Oil & Gas New Major Capital Projects: Developed Versus Undeveloped Regions
Authors: Welsh Rick
Published: June 2014

An environmental and social impact assessment (ESIA) is typically a regulatory, and often internal company, requirement for global oil and gas (O&G) new major capital project (MCP). Health Impact Assessment (HIA) is generally less understood, yet is also becoming a common requirement for global O&G MCPs. A common acronym now is environmental, social and health impact assessment (ESHIA). HIA generally refers to potential health impacts to nearby local communities (e.g., refer to the International Finance Corporation (IFC) Performance Standards). Worker ("inside the fence") health and safety if typically not a part of the ESHIA process, and is addressed under separate processes. That said, there are great differences between HIAs in developed versus undeveloped regions of the world. In developed regions of the world, ESHIAs for unconventional O&G are typically focused on characterization of preexisting baseline conditions and continued monitoring of those conditions during and after O&G operations. For example, many regions now have groundwater baseline and monitoring requirements for unconventional and conventional O&G developments. In contrast, global O&G developments often occur in remote, undeveloped regions. Here, the focus for the social and health impact assessment is typically on impacts to the nearby communities, potentially sensitive populations, and particularly aboriginal groups. An example would be the influx of thousands of workers during construction phase and the potential introduction of communicable diseases into the local communities. Hypothetical case studies will be presented to further explore these topics.
Organizational Ownership of an Interdependent HSE Culture Yields Quantifiable HSE Performance
Authors: Breitsprecher K. , Ndahbros S. , Hinton J. J. , Jacques P.
Published: June 2014

A major oilfield service company began the journey to create a stronger safety culture in its organization. This journey was rooted in the belief that if a company has a mature, interdependent HSE culture, its employees are more likely to recognize and act upon hazardous work conditions than at a company without this culture. It was also firmly believed that HSE leadership skills and operational HSE ownership are important tools in achieving this HSE culture shift. Therefore, to facilitate the cultural shift, an HSE leadership program was developed and instituted.

This paper describes the case study of the Africa region of this oilfield service company following a two-year time period of implementing the HSE Leadership Program. It was expected that the implementation of the HSE Leadership program would lead to HSE culture improvements and furthermore result in HSE performance improvements. Results of the program implementation were highly successful. In addition to a genuine concern for the employee workforce from senior and middle managers, the performance improvements have been remarkable in both leading and lagging indicators.
Factors Controlling the Simultaneous Propagation of Multiple Competing Fractures in a Horizontal Well
Authors: Shin Do H. , Sharma Mukul M.
Published: June 2014

The use of multiple clusters per stage can reduce the number of stages needed to place a given number of fractures in a horizontal wellbore. However, there is concern that some of the perforation clusters may not propagate fractures at all as the fractures compete for frac fluid and fracture width. In this paper, the influence of various hydraulic fracturing design parameters and in-situ conditions on the resulting fracture dimensions and propagation patterns is studied. A 3D geomechanical model was built using ABAQUS to simulate the propagation of multiple competing fractures in a horizontal well. The reservoir was modeled as a porous elastic medium using pore pressure stress elements, and a plane of pore pressure cohesive elements was inserted at each perforation cluster to model fracture propagation. Also, flow distribution among perforation clusters was simulated using a parallel resistors model.

Using this model, a number of simulations were run with a combination of perforation cluster spacing, number of perforation clusters, fracture height, frac fluid viscosity, pumping rate, Young's modulus of the target formation, and formation heterogeneity. The results demonstrated that increasing perforation cluster spacing or decreasing the number of perforation clusters reduced stress interference between the fractures, and more fractures propagated. A high frac fluid viscosity increased fracture widths and led to more stress interference. Higher pumping rates led to longer and wider fractures, and to an increase in the number of propagated fractures. Thicker target formations and taller fractures required wider perforation cluster spacing. Additionally, a higher Young's modulus of the target formation led to more fracture interference, suggesting wider cluster spacing. Lastly, the introduction of any degree of heterogeneity significantly altered the fracture propagation patterns noted above.

Based on the results of these simulations, the following recommendations are made. First, there exists an optimum number of perforation clusters per fracture stage. This optimum depends primarily on the fracture design, the stage spacing and the mechanical properties of the formation. Second, slick water fracs have a better chance (compared to more viscous fluids) of propagating uniform multiple fractures when closely spaced multiple perforation clusters are used. Third, higher pumping rate should be adopted to ensure that a fracture propagates from all perforation clusters. Fourth, even small scale heterogeneities should be considered, as they can significantly alter the fracture propagation pattern. Lastly, when the target formation is relatively thick or has a high Young's modulus, a wider fracture spacing, a higher pumping rate, and a lower viscosity frac fluid should be used.
Using Distributed Optical Sensing to Constrain Fracture Models and Confirm Reservoir Coverage in the Permian Basin
Authors: Holley E. H. , Jones T. A. , Dodson J. , Salazar J.
Published: June 2014

Low-permeability basins present a tremendous challenge to effective completion and reservoir drainage, especially in known heterogeneous environments that present additional complexity. Several robust diagnostic techniques exist in the market currently that are identified as guides to improve completion and stimulation efficiency in basins that require hydraulic fracturing to make low-permeability environments viable. Some of these techniques include fracture modeling, microseismic mapping, diagnostic fracture injection test (DFIT) analysis, radioactive and chemical tracers, and pressure matching. During the past decade, fiber-optic sensing has been identified as an additional tool that can provide significant benefit to complement the more traditional approaches listed previously. In current commercial applications, this includes distributed temperature sensing (DTS), distributed acoustic sensing (DAS), distributed strain sensing (DSS), and optical point pressure and temperature solutions that can define wellbore characteristics through the entire well life cycle.

This case study focuses on optical data acquired from a vertical well drilled in Ector County, Texas in the Permian Basin. The well was stimulated using a limited entry approach as a cased and cemented completion. The project attempted to resolve questions pertaining to the distribution of stimulation fluid to each interval, total hydraulic height growth association to each stimulation treatment, and total production contribution from each interval. This paper focuses on using the fiber-optic results in conjunction with other tools to define the stimulation treatment and completion effectiveness.

A fiber-optic cable was deployed permanently behind the casing to acquire both DTS and DAS data during stimulation treatment, flowback, and production to review the entire well life cycle. Complementing the distributed optical measurements, fracture modeling was performed using data acquired by fiber optics to constrain the model, as well as openhole logging results to compare to the distributed optical results. A review of the post-job fracture model was compared to the DTS fracture height estimates. If a large discrepancy was observed between these two values, the post-fracture model was revisited to assess if other interpretations of the fracture model were reasonable. Distribution of fluid along the near wellbore was also assessed using DTS results to define hydraulic fracture height growth.
Actual and Optimal Hydraulic Fracture Design in a Tight Gas Reservoir
Authors: Zhang T.. , Pang W.. , Du J.. , He Y.. , He Q.. , Liu H.. , Feng X.. , Song B.. , Ehlig-Economides C. A.
Published: June 2014

Designing hydraulic fracture stimulation to optimize well productivity requires knowledge of the initial reservoir pressure and permeability, the closure stress magnitudes in the reservoir and in bounding formations, a carrier fluid with a suitable leakoff coefficient, and rock properties such as the Young's modulus and the Poisson ratio that can be determined from a core sample. When key parameters are left unknown, the hydraulic fracture stimulation is likely to be severely suboptimal.

This study integrates pressure buildup and production transient analyses with microseismic surveys and the recorded pumping schedule to estimate the above-mentioned parameters in previously fractured wells on production for up to 7 years from a tight gas reservoir.

The first well drilled and completed in the block included a pressure buildup test that enabled accurate estimation of the initial reservoir pressure and permeability. A post-fracture buildup test was also conducted, and annual pressure buildup tests in 6 subsequent years showed continuous changes in the fracture morphology with fracture conductivity decreasing by a factor of 3 and fracture length increasing by about 50%. Many of the subsequent wells were drilled in 2 pattern well clusters, each designed to account for fracture propagation behavior indicated from a microseismic survey. A comparison with an optimal hydraulic fracture design intended to maximize well productivity indicates that most of the well stimulations were suboptimal with rate and cumulative production about ½ that of an optimized design based on the same proppant mass.

The observed changes in fracture conductivity and length over time were unanticipated. Because such data are rarely recorded the variations in fracture morphology may be fairly typical and should be of considerable interest to pressure transient analysts. The production data analysis shows the difficulties in determining formation and fracture parameters when the transient response lacks radial flow. The fracture treatment analysis shows a comparison between the actual fracture treatment and one designed to maximize well productivity and clearly illustrates the potential for well improvement using modern hydraulic fracture design principles.
Effect of Dissolved Solids on Reuse of Produced Water and Proppant Handling in Hydraulic Fracturing jobs in Tight Sand Gas Reservoirs
Authors: Haghshenas Ashkan , Nasr-El-Din Hisham A.
Published: June 2014

Hydraulic fracturing is the most common stimulation treatment in unconventional resources. One of the most important challenges in fracturing operations is the large volumes of water consumption and waste water disposal. Environmental and economical attributes of flowback fluids in the oil industry make water treatment an inevitable decision. Applications of produced water in hydraulic fracturing jobs result in low quality fracturing fluid. This is especially true for flowback fluids, which contain high polymer loading. Currently, no practical operating range for produced water content is available, and applied methods are individually developed for specific jobs.

This paper focuses on the analysis of the dissolved solid contents of produced water, which affects the application of flowback fluids and the capability of prepared fluids in proppant transport and handling. A series of laboratory experiments were conducted on a high-pH borate crosslinked guar-based polymer to determine the effects of salt species on the prepared polymer, ranges of acceptable salts contents, and ability to transport proppant. For this purpose, analyses of 36 flowback fluid samples from the West Texas region have been collected, and the maximum and minimum values of all of the contents have been determined to investigate the impact factor of each component. Dynamic rheology tests, traditional changing shear rates, the steady-shear viscosity, and small-amplitude oscillation rheology, were the methods used to evaluate prepared samples.

The prepared polymer shows high sensitivity to the change of some ions such as calcium and magnesium, and the maximum acceptable values were lower than 90% of reported ones in field analysis. Some others such as sodium and potassium were tolerable at higher concentrations, and more than 70% of samples do not need to be treated for these ion contents. On the other hand, there are other ions in different samples, which have ranges of concentrations that were very similar at low concentrations. Although no significant variation in fracturing fluid properties were detected when the different concentrations of them were applied in experiments, their presence can affect post-treatment jobs. The fluids prepared with the determined ranges of dissolved solids showed reasonable rheological stability and proppant handling characteristics.
MPD Automation and Competency: Meeting Training Challenges for New Technologies
Authors: Johnson Austin , Orbell Charles , Leuchtenberg Christian
Published: June 2014

The general form of drilling rigs has remained relatively unchanged for decades. Yet equipment, systems, and methods of a modern rig would be unrecognizable to crews of 20 years ago. In structured tasks, manual controls have largely yielded to automated control systems that require minimal crew intervention. Automation has increased the feasibility of many projects through the use of managed pressure drilling techniques which were previously impractical, if not impossible. But this separation of crew from manual controls, especially with the introduction of new MPD methods, has changed the role of the operator and has invited questions regarding competency and how it is achieved.

Automation has benefitted the industry, but to properly adjust to these changes, it must be recognized that the role of the driller and crew has changed not only in degree but also in kind. This paper is meant to highlight the growing gap between conventional and future competency requirements by discussing new challenges which exist between the driller and the rig brought on by automation as well as difficulties related to the expanded use of new MPD methods. Similarities exist with pilot awareness in the aviation industry that will be discussed along with potential solutions. However there are a unique set of challenges will be addressed which face the drilling industry presenting greater difficulty. Ultimately, a portrait of a future competency program will be presented.
A Simple Transient Flow Model for MPD and UBD Applications
Authors: Udegbunam John Emeka , Fjelde Kjell Kåre , Evje Steinar , Nygaard Gerhard
Published: June 2014

Transient flow models play an important role in the planning and follow-up of advanced well operations such as managed pressure drilling and underbalanced operations. The most recent trend is a situation whereby flow models and control engineering algorithms are combined in various settings, to control flow parameters. This requires robust flow models and an in-depth understanding of uncertainties in the modeling process.

This paper presents a simple and robust transient model that can handle highly dynamic flow systems. The model, AUSMV scheme, has been developed for academic and training purposes. With the model, students can investigate different flow scenarios and pressure control challenges encountered in general well control, managed pressure drilling, underbalanced drilling, and automation.

The capability of this model to handle highly changing flow scenarios will be demonstrated with examples taken from managed pressure drilling and underbalanced operations. The effect of numerical dissipation on the model predictions will be briefly discussed.
Pressure Normalization of Production Rates Improves Forecasting Results
Authors: Lacayo Juan , Lee John
Published: June 2014

Recently, as a result of the increasing exploration and production activity in unconventional plays, new decline curve models have been developed. The main purpose of these newer models—e.g., SEPD, Duong, Logistic Growth, Power Law, Dual-Models—is to overcome the boundary-dominated flow assumption required for validity of the basic Arps’ model, which restricts its application in ultra-low permeability reservoirs exhibiting long-duration transient flow. These new decline curve analysis (DCA) methods are still ordinarily applied only to rate-time data, and thus rely on the assumption of stable (constant) flowing pressure. Since this stabilized state is not reached rapidly in most unconventional wells, the applicability of these methods and the reliability of their forecasts may be compromised. In addition, production performance predictions cannot be disassociated from the operational constraints that existed when production history was observed.

This paper introduces a modified decline curve analysis method we call Pressure Normalized Decline Curve Analysis (PN-DCA) to provide a solution to these problems. Unlike traditional DCA methodology, which analyzes only production rates, this method analyzes pressure-normalized rates. To validate the applicability of this technique, we used hindcasting analysis of real production data from four different shale plays in the US (Eagle Ford, Woodford, Marcellus and Bakken). We found that this technique can be used as a reliable production forecasting technique suited to interpret unconventional well data in specific situations such as unstable operating conditions, limited availability of production data (short production history), and high-pressure, rate-restricted wells. Moreover, this method has proved to have the important ability to dissociate the estimation of future production performance from past operation constraints.

This work also proposes an innovative decline curve analysis workflow, which includes a multi-method approach to optimize the flow regimes identification process. This methodology integrates different diagnostic plots that have been improved by incorporating important concepts such as MBT, pseudo-variables (for gas wells) and pressure-normalized rates. Each DCA model has been designed assuming specific flow regimes. Therefore, a proper identification of dominant flow regimes will help us to perform decline curve analyses with more confidence and to avoid unrealistic production forecasts.

In general, incorporating pressure-normalized rates in decline curve analysis offers the possibility of producing improved forecasting results, which implies greater accuracy in production performance predictions and more reliable reserves estimations. The petroleum industry may become more confident in reserves estimates, which are the basis for the design of development plans, investment decisions, and valuation of companies’ assets.
Improvement of Eagle Ford Shale Formation's Water Imbibition by Mineral Dissolution and Wettability Alteration
Authors: Morsy Samiha , Gomaa A. , Sheng J. J.
Published: June 2014

In order to understand the performance of waterflooding in nano-darcy permeability, naturally fractured shale reservoirs, an integrated study of spontaneous imbibition has been performed. In this study, oil recovery during spontaneous imbibition in naturally fractured shale samples was improved using different water formulations. Different water solutions were formulated by adding different amounts of HCl and NaOH to either distilled water or 2 wt% KCl-base brine solution. Eight water formulations, distilled water, 2% KCl brine, low pH HCl solutions (0.74-1.2), and high pH alkaline solutions (11.7-12.4) were examined to recover oil from shale rocks. Reservoir core samples from Eagle Ford shale were used in this study. The samples were 2.54 to 3.81 cm in diameter and 0.762 to 5.08 cm in length. Firstly, we studied the porosity of the used samples using CT Scanning. The average porosity was 1.6% for Eagle Ford shale samples. Secondly, we studied the rock stability and spontaneous imbibtion of the different Eagle Ford samples in distilled water, 2 wt% KCl, low pH solutions (0.74-1.2), and high pH alkaline solutions (11.7-12.4). During the spontaneous imbibition, the maximum oil recovery was 37% for Eagle Ford using pH 0.74 (3 wt% HCl in 2 wt% KCl) and 44% using pH 11.7 (0.1 wt% NaOH in distilled water). The oil recovery was improved by mineral dissolution using low and high pH solutions along with wettability alteration. The rock hardness was significantly affected by using both high and low pH solutions, which resulted in 93-98% loss of its initial value.
From Streamlines to Fast Marching: Rapid Simulation and Performance Assessment of Shale Gas Reservoirs Using Diffusive Time of Flight as a Spatial Coordinate
Authors: Zhang Yanbin , Bansal Neha , Fujita Yusuke , Datta-Gupta Akhil , King Michael J. , Sankaran Sathish
Published: June 2014

Current industry practice for characterization and assessment of unconventional reservoirs mostly utilizes empirical decline curve analysis or analytic rate and pressure transient analysis. High resolution numerical simulation with local PEBI grids and global corner point grids has also been used to examine complex non-planar fracture geometry, interaction between hydraulic and natural fractures and implications on the well performance. While the analytic tools require many simplified assumptions, numerical simulation techniques are computationally expensive and do not provide the more geometric understanding derived from the depth of investigation and drainage volume calculations.

We propose a novel approach for rapid field-scale performance assessment of shale gas reservoirs. Our proposed approach is based on a high frequency asymptotic solution of the diffusivity equation in heterogeneous reservoirs and serves as a bridge between simplified analytical tools and complex numerical simulation. The high frequency solution leads to the Eikonal equation which is solved for a ‘diffusive time of flight’ that governs the propagation of the ‘pressure front’ in the reservoir. The Eikonal equation can be solved using the Fast Marching Method to determine the ‘diffusive time of flight’, which generalizes the concept of depth of investigation to heterogeneous and fractured reservoirs. It provides an efficient means to calculate drainage volume, pressure depletion and well performance and can be significantly faster than conventional numerical simulation. More importantly, in a manner analogous to streamline simulation, the ‘diffusive time of flight’ can also be used as a spatial coordinate to reduce the 3-D diffusivity equation into a 1-D equation, leading to a comprehensive simulator for rapid performance prediction of shale gas reservoirs (Patent Pending, 2013). The speed and versatility of our proposed method makes it ideally suited for high resolution reservoir characterization through integration of static and dynamic data.

The major advantages of our proposed approach are its simplicity, intuitive appeal and computational efficiency. We demonstrate the power and utility of our method using a field example that involves history matching, uncertainty analysis and performance assessment of a shale gas reservoir located in East Texas. A sensitivity study is first carried out to systematically identify the ‘heavy hitters’ impacting the well performance. This is followed by a history matching and uncertainty analysis to identify the fracture parameters and the stimulated reservoir volume. A comparison of model predictions with the actual well performance shows that our approach is able to reliably predict the pressure depletion and rate decline.
Understanding Shale Performance: Performance Analysis Workflow with Analytical Models in Eagle Ford Shale Play
Authors: Samandarli Orkhan , McDonald Beth , Barzola Gervasio , Murray Mark , Richmond Perry
Published: June 2014

Tight oil and shale gas resources produced 29% of total US crude oil and 40% of total US natural gas in 2012 (EIA). Technically recoverable quantities of shale gas and shale oil resources for the US are 665 trillion cubic feet and 58 billion barrels, respectively. Considering the impact of the "unconventional boom" on the economy, it is crucial to understand the production performance of wells to maximize the recovery from shale plays.

The latest advances in Rate Transient Analysis (RTA) provide quick yet robust tools to assess the quality of the Stimulated Rock Volume (SRV) and long term performance of the wells by estimating EURs. The most common challenge in history-matching of production in shale gas/oil wells has been the non-uniqueness of the history-matched parameters. A lot of emphasis has been put on estimation of fracture half-length, which is believed to be a primary driver for the performance of shale gas/oil wells.

Since linear flow is the main transient flow regime in the early life of a hydraulically-fractured shale gas/oil well, a Rate Normalized Pressure (RNP) versus Square Root of Time plot is the most commonly used diagnostic plot for the performance analysis of the wells. A*sqrt(k) or xf*sqrt(k) parameter groups are reported as a proxy for productivity in hydraulically fractured shale/gas oil wells. Besides having permeability as an unknown, the history-match is also sensitive to net hydraulic fracture height, which is one of the inputs to models that must be specified from other sources of information.

This paper presents a novel approach for production performance analysis of shale gas/oil wells, which significantly reduces the non-uniqueness issues that one can have in comparison of performance. Twenty two Eagle Ford Shale wells were analyzed across the trend from lean gas to high-yield condensate to define a workflow that could be applied to other wells in different geologic areas, yet provide consistent comparison of long term performance (EURs).
Field vs Laboratory Polymer Retention Values for a Polymer Flood in the Tambaredjo Field
Authors: Manichand R. N. , Seright R. S.
Published: June 2014

During a polymer flood, polymer retention can have a major impact on the rate of polymer propagation through a reservoir, and consequently, on oil recovery. A review of the polymer-retention literature revealed that iron and high-surface-area minerals (e.g., clays) dominate polymer retention measurements in permeable rock and sand (>100 md). A review of the literature on inaccessible pore volume revealed inconsistent and unexplained behavior. A conservative approach to design of a polymer flood in high-permeability (>1 darcy) sands would assume that inaccessible pore volume is zero. Laboratory measurements using fluids and sands associated with the Sarah Maria polymer flood in Suriname suggested polymer retention and inaccessible pore volume values near zero. A procedure was developed using salinity-tracer and polymer concentrations from production wells to estimate polymer retention during the Sarah Maria polymer flood in the Tambaredjo reservoir. Field calculations indicated much higher polymer retention values than lab tests, typically ranging from ~50 to 250 μg/g. Field cores necessarily represent an extremely small fraction of the reservoir. Because of the importance of polymer retention, there is considerable value in deriving polymer retention from field results, so that information can be used in the design of project expansions.
Field vs. Laboratory Polymer-Retention Values for a Polymer Flood in the Tambaredjo Field
Authors: Manichand R.N.. N. , Seright R.S.. S.
Published: June 2014

During a polymer flood, polymer retention can have a major impact on the rate of polymer propagation through a reservoir, and consequently on oil recovery. A review of the polymer-retention literature revealed that iron and high-surface-area minerals (e.g., clays) dominate polymer-retention measurements in permeable rock and sand (>100 md). A review of the literature on inaccessible pore volume (IAPV) revealed inconsistent and unexplained behavior. A conservative approach to design of a polymer flood in high-permeability (>1 darcy) sands would assume that IAPV is zero. Laboratory measurements using fluids and sands associated with the Sarah Maria polymer flood in Suriname suggested polymer retention and IAPV values near zero [0±20 μg/g for retention and 0±10% pore volume (PV) for IAPV]. A procedure was developed using salinity-tracer and polymer concentrations from production wells to estimate polymer retention during the Sarah Maria polymer flood in the Tambaredjo reservoir. Field calculations indicated much higher polymer-retention values than those from laboratory tests, typically ranging from approximately 50 to 250 μg/g. Field cores necessarily represent an extremely small fraction of the reservoir. Because of the importance of polymer retention, there is considerable value in deriving polymer retention from field results, so that information can be used in the design of project expansions.
Design, Implementation and Early Operating Results of Steam Injection Pilot in already CO2 Flooded Deep-Heavy Oil Fractured Carbonate Reservoir of Bati Raman Field, Turkey
Authors: Sahin Secaeddin , Kalfa Ulker , Uysal Serkan , Kilic Harun , Lahna Hakki
Published: June 2014

With initial heavy-oil in place of 1.85 billion barrels, the Bati Raman Field (Turkey's largest oil deposition) was discovered and put on stream in 1961. The field hardly attained a primary recovery of ~2% due to the poor quality of the rock and fluid properties, and a low energy drive mechanism. An immiscible carbondioxide (CO2) flooding project commenced in 1986 and it has been successfully implemented for about a quarter of a century. Oil production, which was only 1,500 STB/D prior to this project, reached 14,000 STB/D within a few years, however, there has been a declining trend thereafter.

The project is still active and has added significant value to the field showing an increment of 3-4 times in the recovery factor. Nevertheless, the amount of CO2 required for one extra barrel of oil has a tendency to increase and the fact that the CO2 injection will soon complete its mission, remaining a considerably high amount of oil in the reservoir. Therefore, there is great incentive to implement another effective enhanced recovery process in the field to drain this remaining oil.

Currently, the field is under consideration for another marginal and unique application of enhanced oil recovery, of which no analogous application is yet known worldwide. A steam injection pilot in already CO2 flooded deep-heavy oil fractured carbonate reservoir has been initiated. There are a few similar applications, but their depths are incomparably shallower than the Bati Raman Field. The steam injection pilot with two injectors, one observer, and eleven producers at the crest was commenced in September 2012. The purpose was to heat and pressurize the reservoir from the top and produce oil from the neighboring producers. This paper documents the design, implementation, and early operational results of this pilot project.