bluuebunny/crossref_metadata_2025 huggingface dataset:
Cost-efficient and Improved Treatment Technology for Produced Water Reuse
Authors: Cao Jiasheng , Monroe Stephen , Sun Hong , Li Leiming
Published: September 2015

Produced water reuse for hydraulic fracturing fluids is becoming more attractive for oil and gas completions, especially in areas with limited access to fresh water. However, components in produced water such as suspended solids, bacteria, and certain ions (boron, iron, etc.) may reduce fluid stability or cause formation damage. This paper presents a cost-efficient and innovative system for produced water treatment and reuse along with a comparison with traditional technologies.

The presence of iron and boron is common in produced water. Iron may cause formation damage by forming iron sulfide scale and interfere with proper gel formation in cross-linked fracturing fluids. Excess amounts of boron can interfere with crosslinking reactions in fracturing fluids, causing them to crosslink prematurely or excessively. The constant fluctuation of these components makes it challenging to apply a single technology or traditional technology for efficient treatment. The new system presented in this paper has a unique design and combines several technologies to overcome these limitations.

Traditional methods for iron removal, such as oxidation or pH increase, can be compromised by the high level of hardness in produced water. Accurate real-time analysis is required to adjust the dosage of the chemicals applied, resulting in extra costs. Traditional chemical methods for boron removal need large volumes of chemicals and generate considerable amounts of waste. Conventional boron-selective resins have shown high efficiency for reducing boron concentration, but the hydrocarbons and suspended solids in produced water limited this method's efficiency. With the new innovated process, lab scale testing and a field trial have demonstrated efficient boron removal from over 120 mg/L to below 5 mg/L, allowing a conventional delayed cross-linked hydraulic fracturing fluid to be successfully prepared using 100% treated produced water. In addition, this technology has been demonstrated to be faster and more efficient in iron reduction than traditional methods. Iron removal from a level greater than 900 mg/L to less than 5 mg/L from high-concentration oil contained water was achieved with less than 5 minutes of contact time. This new process exhibited significant bacteria control capabilities as well, reducing the risk of bacteria-caused formation damages that can result in a loss of well productivity, corrosion, or HSE issues.

Compared with traditional technologies, this new method has exhibited cost-efficient remediation of produced water, especially in the removal of iron, boron, suspended solids and bacteria, using minimal amounts of chemicals and generating a relatively small waste stream.
Using Eco-Friendly Biodegradable Materials For Designing New Completions and Re-fracturing Acidizing Applications in which Diversion And Zonal Isolation Enhance Efficiency
Authors: Babey Andrew , Schmeltz Peter , Fragachan Francisco
Published: September 2015

The use of mechanical diverters in the oil and gas industry has been common practice for decades. Perforation ball sealers, degradable balls, rock salt, dissolvable flakes, and downhole equipment such as sliding sleeves or straddle-packer systems are typical means for diversion. With the industry striving to grow more efficient, there is a need for a more permanent and reliable technology that can be deployed with ease and will seal previously stimulated perforations from untreated perforations. This paper will present a case history from two wells in the Wasatch and Green River formations that were treated with degradable diversion materials applicable at a broad bottom-hole temperature range. The diversion material used in both wells maintained its integrity under testing pressures and remained in place for the duration of the well completion operations.

Biodegradable materials are applicable for multiple scenarios: zonal isolation for horizontal wells with multiple perforation clusters, through-tubing treatment of vertical wells in which bridge plugs cannot be used, sealing off perforations for re-stimulation treatments, and sealing off zones during lost circulation.

The results from the two case-study wells treated in the Wasatch and Green River Formations provide compelling evidence that mechanical bridging agents can effectively replace bridge plugs and maintain zonal isolation in both new and re-fracture acidizing treatments. The concentrations of the diverter system blends were optimized during the treatments and achieved typical pressure increases of 200 to 600 psi per stage and completely sealed off the wellbore at pressures above 4,200 psi. The information presented in this paper will show the capabilities of using this material and the potential applications for multi-stage acid stimulation treatments. The pressure responses from the treatments and dissolution studies at specified temperatures show the ability of the materials to remain in place throughout the treatment of the well. The details of the successful treatment execution and the production results will be presented. The results of the case-study wells also show great advantages in both production and operational efficiency.
A New Model for Hydraulic Fracture Growth in Unconsolidated Sands with Plasticity and Leak-Off
Authors: Lee Dongkeun , Cardiff Philip , Bryant Eric C. , Manchanda Ripudaman , Wang Haotian , Sharma Mukul M.
Published: September 2015

Hydraulic fracturing in unconsolidated or poorly consolidated formations has been used as a technique for well stimulation and for sand control. Although a large number of hydraulic fracturing operations have been performed in soft formations, the exact mechanisms of failure and fracture propagation remain an unresolved issue. Conventional hydraulic fracturing models based on the theory of linear elastic fracture mechanics (LEFM) often lead to inaccurate results because large inelastic deformations and strong fluid-solid coupling are neglected in such models.

A fully three-dimensional hydraulic fracture growth model for soft sands is developed. Our model can simulate non-planar fracture growth in poro-elasto-plastic materials, fluid flow inside the fracture with proppant transport, and fluid leak-off from the fracture to the porous reservoir. This paper presents the formulation and implementation of a new model. The model is verified by comparisons with analytical solutions. The model predicts considerably higher net fracturing pressure due to plasticity, which is consistent with observations from the field and laboratory experiments. This is because the stress concentrations at the crack tip in a plastic material are lower than in an elastic material and the plastic yielding shields the tip from the fracturing pressure. This induces shorter and wider fractures than without plasticity. Also, fluid leak-off and the pore pressure diffusion in the reservoir are computed numerically in this model. Higher leak-off leads to a poroelastic backstress that builds up around the fracture and results in shorter fractures.
Water-Swellable Elastomers for Heavy Brine Environments
Authors: Wang Xiao , Sadana Anil K. , Mathur Vipul
Published: September 2015

Swellable packers are widely used to create annular seals between production casing and an open hole. The popularity of swell packers is due to their ease of deployment and streamlined design, which does not have moving parts to malfunction. The current water swell packer technology meets the swelling requirement in light monovalent brines, however, falls short of swelling requirements in heavy brines and especially divalent brines like CaCl2 and CaBr2. This work/paper presents the development of new swellable elastomers that exhibit superior swelling in divalent brines and enhanced mechanical properties compared to existing swellable compounds.

New swellable elastomers are made by blending newly developed swellable nanocomposite microgels with nitrile butadiene rubber (NBR). Nanocomposite microgels possess a unique polymer/nano-clay network structure in which nano-clay acts as a multifunctional cross-linker and leads to the formation of higher molecular weight polymer chains. As a result of the unique structure, the nanocomposite microgels exhibit better elastomeric behavior, higher swelling ratio and faster swelling kinetics compared to the conventional super absorbent polymer (SAP). The nanocomposite microgels were synthesized through the reverse-phase suspension polymerization method to achieve a gel particle size of less than 10 μm, which is essential for the fast swelling rate of the compound. A divalent brine-tolerant 2-acrylamido-2-methylpropane sulfonic acid (AMPS) monomer was selected for the synthesis to achieve divalent brine-swelling capability.

The new swellable elastomers exhibit a 100% volume increase within three days in 10% CaCl2 at 200° F, and a final volume swell of more than 200% for a 1-in. button sample. This volume swell of the button sample is four times higher than the current water swellable elastomers. The new swellable elastomers also exhibit better mechanical properties than current swellable compounds.

Newly developed swellable elastomers made by incorporating novel nanocomposite microgels in the base polymers offer swellable packers for heavy brine environments.
Integrated Production Logging Approach for Successful Leak Detection Between Two Formations: A Case Study
Authors: Al-Mulhim Abdullah , Al-Thwaiqib Ibrahim , Bogari Abdulkader , Bawazir Mustafa , Abdein Moutaz
Published: September 2015

A major exploration and production (E&P) company is acquiring a significant number of multiphase production logs a year for reservoir management. It is anticipated that this number will increase, when these deviated and horizontal wells start to produce water. It is more challenging when these wells become dead due to downhole communication between an aquifer and the objective reservoir resulting in excessive downhole water dumping. The strategy, therefore, is to run advanced production logging tools (APLT) integrated with the pulsed neutron logging tool (PNLT) to provide velocity along with holdup maps across the diameter of the borehole from an array of sensors and water velocities inside the wellbore or the annulus, respectively. The combination between APLT and PNLT data provides accurate detection and quantification of water zonal contributions.

The aim of the three case examples presented in this paper is to facilitate detecting the leak point and assembling the inflow profiles. The first example is an open hole completion. The logging data showed 1000 bbl of down-flow movements in the tubing-casing annulus (TCA) starting from the shallow aquifer. The second well was completed with an inflow control device (ICD). Water dumping was observed from the leak over the blank pipe down to the screen interval, which is also supported by temperature deflection. The third example is a cased-hole perforated completion. An integrated logging approach yielded reliable results in detecting the water entry interval, and the water entry was identified from the perforated section flowing upward to the casing leak. This detected crossflow in the mentioned examples at shut-in conditions was the reason that the wells were dead.

The established integrated logging solution and field examples showed evidence that a leaking interval was suspected to be responsible for high water cut, reducing well performance and killing the wells. The source of water production identified provides the justification for a workover to isolate the water entries, secure the objective reservoir, and revitalize the dead well.
Optimizing Unconventional Asset Development and Reserves Confidence With Portfolio Tradeoff Analysis
Authors: Kostuik K. , Mu Y. , Parma R. , Wearly J. , Rooney K.
Published: September 2015

A multi-objective optimization algorithm was used to develop five-year capital plans for a portfolio of unconventional assets. The approach explored development plan tradeoffs, while considering statistical uncertainty of reserves additions. The objective was to apply the theory of multi-objective methods to an existing planning model, and to evaluate if such methods can provide greater knowledge, faster analysis, and better solutions.

The tradeoff analysis workflow applied recent advances in constrained multi-objective optimization. A hybrid optimization algorithm, combining elements of mathematical programming and evolutionary computation, was used to calculate tradeoff frontiers under varying assumptions and constraints. Portfolio metrics included net present value, capital, reserve replacement ratio, capital effectiveness, production, reserves, and well counts. Statistical metrics were used to calculate uncertainty bounds (P10 and P90) on portfolio reserves additions, plus confidence factors for achieving given reserves targets. Constraints on drilling activity by area over time were also applied.

The optimization algorithm successfully calculated tradeoff frontiers and efficient portfolios. The approach showed how tradeoff frontiers change with varying assumptions and constraints, and provided knowledge of strategic opportunities and limitations. The model enabled rapid replanning as objectives, constraints, and source data changed. The optimizer delivered better solutions than the previous planning model, and helped to identify short lists of optimized capital plans faster than otherwise possible. Reserves uncertainty metrics quantified the tradeoff between reserves targets and reserves confidence. The analysis revealed weaknesses of published uncertainty methods, and highlighted possible improvements for future research.
Root Cause Analysis of Drilling Lost Returns in Injectite Reservoirs
Authors: Buechler Scott , Ning Jing , Bharadwaj Nidheesh , Kulkarni Kaustubh , DeValve Caleb , Head Timothy , Mols Arnout
Published: September 2015

Identifying the root cause of drilling failures can often be challenging due to uncertainty in whether drilling failures were a result of lost returns leading to borehole instability and pack off, or ineffective hole cleaning leading to lost returns, pack off, stuck pipe, and eventual well failure. Such an analysis is further complicated when losses occur over a wide range of equivalent circulating densities (above and below predicted fracture gradients), well angles, and hole sizes. The work presented combines a fundamental physics approach with field data to identify the root cause of drilling failures in Paleocene and Eocene injectite sand intervals. The field data consisted of image and conventional log data, downhole equivalent circulating densities (ECD), loss rates, leak off tests, and formation integrity tests. Study results showed that unfavorably oriented sand-shale interfaces, which can occur more frequently at the top of an injectite reservoir, can re-open at ECDs below predicted fracture gradients, but above the minimum stress, and result in massive losses. The physical model is shown to correlate well with field data supporting the conclusion of lost returns being the root cause for observed drilling failures. Complimentarily, proprietary transient hydraulics and hole cleaning models showed that fluctuations in drilling parameters (flow rate, ROP, etc.) leading to suboptimal hole cleaning at a specific location along the wellbore were not able to generate significant enough pressures to result in observed losses if ECD at the bit was managed within the anticipated fracture gradient. By identifying the root cause of drilling challenges, potential solutions can be applied to include revised fracture gradients, operational hole cleaning parameters, drilling techniques, and well path planning to reduce overall drilling risk. These results will allow for informed trade-offs between reduced drilling risk and future production volumes.
Functional Approach to Data Mining, Forecasting, and Uncertainty Quantification in Unconventional Reservoirs
Authors: Grujic Ognjen , Da Silva Carla , Caers Jef
Published: September 2015

The difficulty in applying traditional reservoir simulation and modeling techniques for unconventional reservoir forecasting makes the use of statistical and modern machine learning techniques a relevant proposition for shale systems. However, the most current applications of these techniques often ignore the systematic time variations in production decline rates. Traditional decline curve modeling techniques fall short in predicting actual physical parameters and are highly dependent on the assumed physical model.

In this paper, we propose a non-parametric statistical approach, more specifically, using a modern technique termed functional data analysis (FDA). In FDA production data is modeled as a time series composed of a sum of weighted smooth analytical basis functions. Instead of assuming a model, this technique allows us to learn the model from the data by jointly fitting all production profiles in the field. Principal component analysis can be applied to the functional data, termed (fPCA). Applying fPCA to declining rates from many wells, transforms time varying data into lower-dimensional score data. We found that in the real field data studied, 2-3 such functional principal components were sufficient to describe the entire production in a shale play. Low dimensional score data is also very valuable for data mining and sensitivities studies that enable better understanding of production drivers. Finally, building regressional relationships between geological and completions parameters and functional principal component scores enables forecasting production at new well locations with new sets of geological and completion parameters.

Proposed methodology is demonstrated on a real reservoir case study with 172 horizontal and hydraulically fractured wells. Wells originate from one of the most prolific shale plays in North America, and have been in production for at least 500 days. Case study was focused on oil production rates, and obtained forecasting error over multiple test sets (100) was 21% (on average).
Development Best Practices in the Duvernay Liquid Rich Shale - Early Stage Sensitivity Analyses and Comparative Economics for Decision Making
Authors: Braun David , Gurden Catherine , Yang Wu , MacGregor Alex
Published: September 2015

To maximize the development value of the emerging Canadian Duvernay liquid rich shale (LRS) play quality risk-based decisions need to be made. These decisions must consider a number of complex variables that can all have a high impact on both short and long term economic viability. Credible ranges for variables such as well construction costs, production decline rates, infrastructure configurations, and commodity prices (e.g. oil price volatility witnessed in 2014) must be built. Quality decisions can then be made by leveraging a detailed understanding of the variables’ interdependencies and quantified economic impacts.

This paper describes the construction and analysis of a suite of Duvernay scenarios developed by Shell Canada using sophisticated hydrocarbon planning software. They were built using a strategy table approach and focused on options for gas processing facilities. The impacts of drilling ramp-up timing, shallow cut versus deep cut configurations, and operator versus midstream build-own-and-operate (BO&O) were examined. For example, several midstreamers exist in the Duvernay play area with significant, non-optimal (sour and shallow cut) processing capacity. These facilities can be used today to capture initial value but require expansion in the future; therefore, an evaluation of all credible new build options is required to understand how best to develop the play.

A suite of key comparative economic metrics, including net present value (NPV), profit to investment ratio (PIR), and payout period (POP), was generated. Expected monetary values (EMV) for each scenario were calculated and used to identify the optimal, risk-based approach. Additional insights were derived by comparing the scenarios, these insights included: the value of information associated with a longer appraisal period, the value of infrastructure flexibility, and the NGL recovery and product price thresholds required to justify deep cut construction.
Is Pumping Large Volume Sand Frac Treatments Sustainable?
Authors: Shelley Robert* P. , Shah Koras , Guliyev Nijat , Mohammadnejad Amir , Sheludko Stanislav
Published: September 2015

Mud rock “shales” by their very nature can be problematic to fracture stimulate given the wide variation in geology, rock properties and reservoir characteristics. Quite often, a positive production response from a well may be incorrectly credited to the completion and frac design when in reality the production was dominated by favorable reservoir characteristics. Conversely a poor production response from a well may be blamed on the completion and frac design when in fact poor reservoir quality is the controlling factor. The subject of this paper is a revisit of the physics behind production increases from hydraulic fracturing and results from detailed evaluations performed by experienced engineers with reservoir knowledge for the purpose of evaluating completion effectiveness and frac efficiency for shale and other low permeability formations.

The findings presented show that in many cases pumping large volume sand frac designs result in an inefficient hydraulic fracture. This inefficiency is due to minimal production contribution from a relatively large portion of the hydraulically exposed fracture face and/or frac length. These findings are supported by current hydraulic fracturing theory and understanding. The evaluation methods utilized in these evaluations are not new, however they currently are under-utilized by the industry for completion and frac analysis.
Fracture Diagnosis in Multiple Stage Stimulated Horizontal Well by Temperature Measurements Using Fast Marching Method
Authors: Cui Jingyuan , Yang Changdong , Zhu Ding , Datta-Gupta Akhil
Published: September 2015

Downhole temperature measurements is one of the solutions to understand downhole flow conditions, especially in complex well/reservoir domains such as multi-stage fractured horizontal wells. In the past, models and methodologies have been developed for fracture diagnosis for multiple-stage fractured horizontal wells. They are based on either semi-analytical approach for simplicity or reservoir simulation for generality. The challenges are that semi-analytical models are not robust enough to describe complex fracture systems, while numerical simulation is computationally expensive and impractical for routine inversion. To develop a comprehensive approach to translate temperature to flow profile, we adopted Fast Marching Method in simulating both heat transfer and velocity/pressure field in the domain of interest (heterogeneous reservoir with multiple fractured horizontal wells). Fast Marching Method (FMM) is a relatively new approach which is efficient in front tracking. Previous studies show a significant success in the investigation of pressure depletion behavior and shale gas production history match. By the nature of heat transfer in porous media, the thermal front propagation would lag behind pressure and the noticeable temperature change in reservoir only happens near hydraulic/natural fractures. FMM can be used to efficiently track the heat front that is associated with flow field.

In this study, we solve the thermal model in porous media by transforming the general energy balance equation into a 1-D equation with a ‘diffusive time of flight’ as the spatial coordinate system. Besides the diffusive heatpropagation, Joule-Thomson effect and viscous dissipation are also considered in the model. The inner boundary of the model is carefully handled and the drainage volume of each fracture is calculated to identify different inflow temperature related to flow rate at perforation locations. The model was validated by a finite difference approach. Examples are presented in the paper to illustrate the application of the new method. The approach can be used to quantitatively interpret temperature measurements to fracture profiles in horizontal wells.
Why “Do Not Disturb” is a Safety Message
Authors: Sweatman R. E. , Mitchell R. F. , Bottiglieri A.
Published: September 2015

Although not disturbing the cement during its curing time is sometimes mentioned in the oil and gas industry's literature and training courses, the information is often not thorough or explicit on how cement can be disturbed during the waiting on cement (WOC) time period and adversely affect safe drilling operations. This has contributed to a lack of understanding of best practices to use and those to avoid by personnel involved in planning, designing, and drilling wells, including those involved in cementing casing and liners and in other associated operations to install annular sealing devices such as setting openhole packers, liner hanger seals, subsea wellhead casing seal assemblies (WCSA), and liner top packers. This paper includes comprehensive information to help rectify this situation.

In addition to describing previously known damage mechanisms and consequences, new ones will be presented such as how the setting of WCSA may have undesirable safety results: a) the drilling fluid level above the cement is blocked so abnormal levels can't be monitored; b) cooling of drilling fluids may change its volume and density causing progressive losses of the fluid column's hydrostatic pressure; and c) formation influx can then initiate to damage the cement.

Thermal modeling with supplemental algorithms and lab tests are used to evaluate whether or not overbalanced pressures are converted into underbalanced ones during WOC times when cement is a fluid and not yet set hard into a pressure barrier.

In an example well where a WCSA was set shortly after the cement job, thermal analysis indicated how flow-able formations became underbalanced within the first two hours of WOC when the cement was still a fluid. After 16 hours later, sufficient pressure differentials built up to breach a mechanical barrier, causing a loss of well control.

Novel information identifies safety risks such as loss of zonal isolation, wellbore integrity, and well control when adverse thermal effects on drilling fluids are combined with setting of annular seals above the top of cement during WOC time periods.
Comprehensive Global Model for Before-Closure Analysis of an Injection Falloff Fracture Calibration Test
Authors: Liu Guoqing , Ehlig-Economides Christine
Published: September 2015

Since the injection-falloff fracture calibration test is generally accepted as a reliable way to obtain several key formation parameters, it is one of the essential parts of hydraulic fracturing design. While several abnormal behaviors have been described qualitatively and are frequently observed in an injection falloff fracture calibration test, the only quantitative model for before-closure behavior accounts only for normal leakoff, which seldom happens in practice. This paper describes several new analytical and semi-analytical models to simulate and quantify abnormal leakoff behaviors such as tip extension, pressure dependent leakoff (PDL), multiple apparent closures and transverse storage.

Based on material balance, we model pressure change with time considering the fracture geometry and leakoff volume under various leakoff mechanisms. Then, we show that the appearance of the modeled mechanisms both on the standard Nolte plot and on the log-log diagnostic Bourdet derivative presentation qualitatively matches behavior seen in previously published field data examples.

Results suggest that the early '/2-slope occasionally observed on the log-log diagnostic plot is probably fracture linear flow. When present it can mask all or part of a wellbore storage effect. Natural fractures have a significant impact on the pressure falloff behavior when they open during treatment. Depending on the properties of the natural fracture system, the pressure response can behave as pressure-dependent leakoff (PDL), transverse storage, multiple closures or even normal leakoff in some cases. In addition, if tip extension or PDL behavior are observed, propagation pressure or natural fissures opening pressure can be estimated respectively.

The global model for the closure behavior combines the flow regime models. When shown on the loglog diagnostic plot, calibration test data reveal derivative trends that are used to estimate parameters to which each flow regime is sensitive. Sensitivity analyses with the new model show relative importance with time of the various model features. This work promotes a complete understanding of the pressure response from various leakoff physics and provides a method to quantify parameters needed for more effective hydraulic fracture design.
Application of Kalman Filter to Predictions of Pore Pressure While Drilling
Authors: Bektas Evren , Miska Stefan Z. , Ozbayoglu Evren M. , Yu Mengjiao , Takach Nicholas , Velazquez-Cruz David , Shahri Mojtaba Pordel
Published: September 2015

Accurate formation pore pressure prediction is the most important requirement for safe and effective drilling. It essentially contributes to the reduction of drilling risks and provides cost-effective drilling of wells. Even though there are methods that rely on well logs, seismic data and effective stress models to predict pore pressure, there is no model available for real-time pore pressure prediction ahead of the bit.

This study explains how to design and apply a steady-state Kalman filter to predict real-time formation pore pressure optimally by combining outputs from both Eaton's model and from Logging While Drilling (LWD). The objectives of this study are to minimize the noise on pore pressure predicted from well logs (or LWD) measurements and to compute the next estimate of pore pressure ahead of bit using only the most recent measurement.

Data obtained from well logs usually have noise measurements. The noise measurements lead to changes of the results acquired from well logs. Therefore, uncertainties occur on the estimated pore pressure. The designed Kalman filter is a recursive data processing algorithm to produce optimal estimate of pore pressure ahead of the drill bit. The estimates tend to be more refined than those based on measurements from well logs alone.

First, Eaton's method, which is one of the most widely used pore pressure prediction methods, was modeled and represented in the state-space form required for Kalman Filter modeling. Parameters used in the Kalman Filter algorithm were also identified in state-space form. A computer code to implement the designed Kalman filter algorithm has been developed. Additionally, field data were used to evaluate the performance of the proposed algorithm.

Based on the results, it is concluded that Kalman filter can be a very effective tool for detecting overpressure zones to avoid drilling problems before entering such zones.

The most important achievement is that the developed algorithm can be used as a design tool in offshore and onshore drilling operations along with real-time LWD data to optimally estimate the formation pore pressure of the next interval ahead of the bit during the drilling operation.
Short-Term Production Operation Management: Continuous Application of an Innovative Integrated Production Optimization Tool
Authors: Scaramellini Sara , Cerri Paolo , Bianco Amalia , Masi Silvia
Published: September 2015

This paper shows the results of routine field application of an innovative tool for the integrated production optimization of surface facilities based on a biogenetic algorithm. Periodical runs of the tool have been performed in order to evaluate changes in configuration of the system or mitigation of possible production losses, allowing the complete exploitation of field potential at each stage of field production life.

The described integrated production optimization tool has the ability to integrate well performances, gathering system calculation, and process plant simulation in a unique environment in order to optimize the field configuration. Thanks to a powerful biogenetic algorithm the searching of the optimum field configuration is performed. Conflicts and interactions between variables, constraints, and operational limitations are balanced and solved holistically by the optimization tool. The operative procedure on the application of integrated modeling production optimization by means of this innovative tool, foresees the run of the model on a periodical basis in order to evaluate possible changes in asset configuration and mitigate production losses associated to workovers or system re-start after possible shutdown.

The integrated production modeling was developed for an on-shore oil field and applied regularly to evaluate different scenarios encountered during its operational life and optimize the field configuration at each stage. This paper illustrates different examples coming from the application of the operative procedure for integrated production optimization modeling. First, results are presented on the application of the tool to mitigate production losses during a workover. After a complete field shutdown, different scenarios were analyzed with the support of the optimization tool in order to evaluate the best configuration during the startup phase. Finally, the optimum desired flow rate was calculated for a gas-lift well in order to maximize the global system production. Results of the simulation were shared with the reservoir department for the management of gas injection rate.

Short-term production operation management is supported by routinely application of the presented innovative tool. The holistic optimization of complex surface systems allows the complete exploitation of field potential and production losses mitigation at each stage of field production life.
Improving Fiber-Optic System Reliability in Permanent Installations
Authors: Blount C. G. , Friehauf K. E. , Smith B. E. , Smith D. P. , Jaaskelainen Mikko , Baldwin C. S.
Published: September 2015

Permanent installation of fiber-optic (FO) sensors, whether discrete or distributed, provides beneficial monitoring of a wide variety of parameters during every stage of a well's useful life—from drilling and completions, through the productive period, up to and including permanent abandonment—assuming that the sensors do not fail during installation or subsequent wellbore intervention operations. Long-term reliability is critical to obtain maximum benefit of FO based sensor installations and is crucial to increased adoption of this technology in the oil and gas industry. FO system reliability depends on several factors and requires diligent attention to numerous details, a responsibility shared by manufacturers, service companies, and oil and gas operating companies.

Unexpected signal degradation of FO cables experienced in several instrumented wells required an engineered program approach to understand the failures and guide system improvement developments. Multiple-wavelength optical time domain reflectometer (OTDR) technology was used to diagnose symptoms of the fiber degradation. The importance and usefulness of OTDR technology was recognized, and a program to monitor fiber “health” with measurements recorded at regular intervals was developed to capture crucial historical records of the fiber/cable performance before system installation, during installation, and after installation. The historical progression of optical signal degradation proved to be invaluable in discerning root causes for this degradation. In the problematic FO cables, OTDR traces suggested various failure modes, including hydrogen darkening, fiber bending, and, in one well, a cable breach.

An enabler to frequent OTDR data collection is the ability to remotely operate the FO interrogation units and OTDR equipment. Travel to remote well locations is costly in terms of travel expenses and personnel. It interferes with accomplishing other tasks and often requires the assistance or presence of field operations personnel for onsite access. The system requirements and components used to remotely operate the onsite FO electronic interrogators in the monitoring program are described in this paper.

Based on the OTDR data, additional testing programs were initiated, new cables were designed and assembled, and quality assurance protocols were added. This paper describes the optical fiber “health” monitoring program, reviews case histories, emphasizes the importance of this diagnostic information, and summarizes developments to improve FO system reliability. Significantly improved reliability has been recognized in current installations and is expected to continue for future permanent installations based on the FO “health” program learnings.
OPEC and Unconventional Resources
Authors: Ashayeri Cyrus , Ershaghi Iraj
Published: September 2015

Crude oil and natural gas have been major pillars of the modern civilization during the past century. They are among the most valuable depletable global resources. The energy market has witnessed many oil price shocks during the past several decades. Such instabilities have impacted the global oil and gas industry in ways that have included disruption of investment in the infrastructure, slowdown of advancements in technology development, and backwardness on attracting and training creative solution providers. OPEC (Organization of Petroleum Exporting Countries) has been partly blamed for instigating such price instabilities. Recently, and since the latter part of 2014, in the fear that the shale resource developments may affect the market share of the OPEC producers, oil prices have dropped significantly because of OPEC countries, while suffering losses to their own economies, flooded the market with cheap oil. The global oil industry is now facing a similar situation it has faced several times during the last three decades.

Advantages and disadvantages of low oil prices for both net exporters and net importers of crude oil, as well as the global economy, have been extensively discussed in the literature. Based on the available statistics, while in the short terms, OPEC producers may regain their market shares by producing low cost conventional oil and discouraging shale oil and gas developments, in the long runs, this might not be a successful strategy. OPEC countries in few decades will be paying a high price when their conventional resources reach to levels barely satisfying their domestic needs. Furthermore, because of current orchestrated low prices for shale resources they are preventing their own countries from investing in the development of unconventional resources in terms of technology, manpower and pace of development. In this study we examine the potential of source rock development in some OPEC countries and discuss the importance of realizing the real value of crude oil when it gets to pricing a depletable resource and considering the substitution cost.
Development And Qualification Of A New High Pressure Gas Tight Rotary Shouldered Connection Incorporating Metal-to-Metal Technology For Deepwater Drilling And Completion Applications
Authors: Bassarath W. , LaFuente M. , Branly R.
Published: September 2015

Deepwater drilling and completions operations particularly in the Gulf of Mexico have a growing need for gas tight connections incorporating a metal-to-metal seal. This has been motivated by wells requiring drill stem testing, high-pressure completions/hydraulic fracturing jobs or managed pressure/under-balanced drilling operations. Safety and well integrity concerns further accentuate the need for a no compromise approach when developing connections with gas tight capability. In response to these industry needs a new gas tight connection with a metal-to-metal rotary seal has been developed. This premium high-pressure connection allows the same drillstring to be utilized for both drilling and completion operations, representing a considerable cost saving and improved efficiency over conventional industry practice.

This paper details the development and qualification of this new double-shoulder gas tight connection for drilling and other drillpipe based applications. Several concepts were assessed by Finite Element Analysis (FEA) and the final solution involved a hybridized version of a premium high torque connection and the connection from a drill-pipe-riser. The connection therefore provides the high pressure capability of premium casing or tubing connections coupled with the robustness and increased torsional strength associated with a double shoulder rotary connection. Qualification of the new product was performed on the most critical sizes and involved industry standard physical testing including make & break, overtorque, combined loading and fatigue testing. In fact, it provides one of the highest operating safety margins of any gas tight connection and is qualified to 30,000 psi internal pressure and 25,000 psi external pressure. Results of the full qualification are presented and discussed below.
CFD Modeling Of WBGT For An Offshore Platform
Authors: Tsai Kuochen
Published: September 2015

A wet-bulb globe temperature (WGBT) model has been incorporated into computational fluid dynamics (CFD) software to assess heat stress for the safety of workers on an offshore platform crowded with oil processing units. The model contains all critical elements needed to model WBGT, including conductive and convective heat transfer from the ambient air, radiative heat from the hot processing unit surfaces, solar load and ambient atmosphere, and the blockage of equipment, pipes and structural frames of the platform.

The CFD model was constructed with geometry files directly imported from 3-D modeling software used for large offshore platform structures. The imported geometry was then extracted for necessary parts critical for the thermal modeling. Smaller features, such as deadleg pipes, nuts and bolts that won't influence the results are removed to reduce computational costs. The parts were then grouped according to thermal boundary conditions to be applied, including temperature, heat transfer coefficients and emissivity. A wrapping mesh was applied to convert the CAD geometry into a meshable domain and mesh was generated with specified sizes that can eliminate small gaps and undesirable features ill-suited for CFD solutions. A WBGT model was incorporated into a commercial CFD software package using an iterative procedure from the work of LilJegren et al. (2008). The inclusion of the WBGT model greatly enhances the predictive capability of CFD models for assessing the heat stress experienced by human operators due to its ease of use without resorting to the modeling of human body surfaces and locations.

The model was carefully verified by comparing the CFD results with explicitly modeled WBGT sensor surfaces and the impact of radiation, wind speed and relative humidity are shown. The modeled results for the offshore platform show that it is necessary to insulate the processing units. The feasibility of such a comprehensive model greatly enhances the understanding of the heat stress distribution and provides new opportunities for remedial actions.
CFD Simulation of Turbulent Flow Structure in Stratified Gas/Liquid Flow and Validation with Experimental Data
Authors: Dabirian Ramin , Mansouri Amir , Mohan Ram , Shoham Ovadia , Kouba Gene
Published: September 2015

Although two-phase stratified flow pattern commonly occurs in petroleum industry the understanding of it, in terms of structure of the wave interface and the ensuing interaction between the two phases, is limited compared to single phase flow. Also, most of the studies have not taken the velocity profile across the pipe cross-section into account, rather just focused on the average velocity of each cross section. This paper will provide a unique insight into these velocity profiles, which are critical for frictional pressure drop calculations and prediction of phenomena such as wall effects of multiphase flow, erosion, corrosion, hydrate formation, wax deposition, etc. The objective of this paper is the analysis of this gas-liquid flow pattern in a horizontal pipe utilizing Computational Fluid Dynamics (CFD) simulation and comparison of the results with experimental data. The scope also includes the investigation of turbulent flow structure beneath gas-liquid interface by calculating the stream-wise velocity profile.

Experimental studies have been conducted to investigate gas-liquid stratified flow in horizontal pipe. A unique experimental facility was constructed with a 4-in ID PVC pipe and measurements were performed utilizing air-water. Liquid level at the center of the pipe is measured by ultrasonic proximity sensor at different superficial velocities of gas and liquid. Along with experimental tests, CFD simulations for the same test conditions have been performed using a commercial CFD code. For tracking the two-phase interface, Volume of Fluid (VOF) method was applied. The numerical simulation was obtained with the Realizable k-epsilon model of turbulence.

Comparing the CFD simulation results and liquid hold up measured experimentally revealed a good agreement (discrepancy<±15%). The experimental data also show that at constant superficial liquid velocities, the liquid level increases with decreasing superficial gas velocities. The validation of the CFD results with experimental data indicates that, CFD simulation has the potential to be used for facility design and scale-up processes in petroleum industry.