bluuebunny/crossref_metadata_2025 huggingface dataset:
Model-Based Production Optimization of the Rubiales Field, Colombia
Authors: Stanko Milan , Asuaje Miguel , Diaz Cesar , Guillmain Miguel , Borregales Manuel , Gonzalez Diana , Golan Michael
Published: September 2015

This paper describes the challenge of managing and optimizing the production of a large land based oilfield with hundreds of ESP-boosted wells arranged in widely distributed well clusters which production converges to major trunklines traversing the field. The Rubiales field, located in the eastern plains of Colombia has challenging features, characteristics and layout that demand effective model-based production optimization and control. The field's gathering system feeds the commingled production to two central field processing plants.

The flow of the numerous wells and streams of the network are interdependent as there are no gas separation facilities at the clusters or at any other location in the network between the wellhead sources and the entry to the processing plants. This creates an interdependency of well streams. Thus, any production change at a single well affects the pressure and rate of all other wells in the network and consequently the total field production. The water rate from each individual producing well strongly depends on the drawdown and the stage of depletion of that particular well, and how it is controlled by varying the speed of its ESP. High water cuts of most producing wells and the constraints on water treatment and disposal at the field level dictates a need for frequent readjustment of individual well ESP speed.

Adjusting ESP speeds to maximize the field oil production, subject to field water production constraints, must also take into account a variety of additional constraints related to system limitations, ESP performance, power consumption, production operations and reservoir recovery strategy. One cannot rely solely on operational intuition and empirical field practice for individual ESP control. Rather, a model-based optimization system has been implemented, taking into account all field and well constraints. The implemented system is robust, fast and easy to tune. Furthermore, inflow of heavy and viscous Rubiales oil into the horizontal wellbores is driven by a strong and active aquifer in a highly heterogeneous and permeable reservoir. This results in rapid changes of produced water cut in response to small changes in drawdown, demanding effective tuning of a predictable well inflow function for the purpose of optimization.

This paper describes the model-based optimization system employed in the Rubiales field. The system is customized to the large scale and special features of Rubiales, such as the demanding production performance of its wells, the constraints of facilities, and the objective to maximize profit given by production revenues less OPEX.
Targeted Perforating in the Granite Wash Based on Traced Cement Spacer Leakoff
Authors: Crawford E. M. , Hodgson T. , Senters C. W. , Woodroof R.A. , Knowles S.
Published: September 2015

Completion diagnostics have been applied in Granite Wash wells in the Texas panhandle and western Oklahoma for decades. When applied in horizontal wells, these diagnostic data have shown that the perforation clusters are not always evenly stimulated. In an effort to place the perforation clusters across desirable reservoir targets, engineered perforating has been utilized. In order to target desirable natural fracture swarms and higher porosity streaks, an effort was made to identify those features by taking advantage of the propensity for completion fluid leakoff to occur into those features immediately prior to pumping cement. If enough differentiation is evident using some form of completion diagnostics, then those features that capture the traced completion fluid can serve as targets for the subsequent engineered perforating. In this paper, gamma-emitting particulate tracers were mixed in the spacer fluid used to separate the drilling mud from the cement with the expectation that this traced spacer fluid would leak off into some of these targeted features, and those tracer captured features could then be identified with a spectral gamma ray logging tool after pumping cement. Subsequently, the proppant used to hydraulically fracture those same intervals could be traced with other gamma-emitting particulate tracers to determine if those targeted features had been successfully fractured. This paper will compare and contrast the spectral gamma ray logs run after circulating the traced spacer fluid and cement and after pumping the traced hydraulic fracturing treatments. The diagnostic data will also be compared with well performance data for these wells.
Dynamic Water Injection Profiling in Intelligent Wells Using Distributed Acoustic Sensor with Multimode Optical Fibers
Authors: Xiao J. , Farhadiroushan M. , Clarke A. , Jacob S. , AlMulhem A. , Milne H. C. , Shawash J. , Parker T.
Published: September 2015

A distributed temperature senor (DTS), that uses a multimode fibre, has been used historically for flow profiling in intelligent wells. In horizontal oil production wells, it is difficult to determine the flow profile due to lack of geothermal gradient. In water injector wells, the DTS can be used to monitor the warm-back temperature changes after the well has been shut-in. If the water injector has been continuously operating over a long period of time, the warm-back may take several days or months, which is not practical.

The intelligent Distributed Acoustic Sensor (DAS) system, that commonly uses single-mode fiber, is a very promising technology for inflow monitoring. In intelligent well completions the acoustic energy generated across inflow control valves (ICVs) and inflow control devices (ICDs) can propagate up through the production tubing. Using an array processing the speed of sound can be measured to monitor the fluid composition. In addition, the flow velocity can be measured by evaluating the Doppler shift between up-going and down-going acoustic waves.

The DAS system was retrofitted to existing optical fibers that were already installed along several wells in Saudi Arabia. The acoustic noise energy generated across the inflow devices and propagating along the wellbore tubing was recorded. The acoustic noise spectrum can be used to monitor the fluid flow through the inflow devices. Using array processing, the speed of sound can be determined over several sections of the tubing to identify the fluid composition and the velocity.

In this paper we report on a horizontal open hole water injector equipped with ICDs. This well was previously instrumented with a multimode fiber for distributed temperature sensor (DTS) measurement. We retrofitted the DAS system to the existing multimode fiber and recorded both amplitude and phase of the sounds waves in real time. The dynamic flow profiles across the ICDs zone were observed as the injection rate was varied from 100% to 31% by changing the surface choke settings. The downhole injection rates were quantified by determining the Doppler shift between up-going and down-going speed of sound propagating along well above the ICDs. A good correlation was observed with a surface flowmeter.

The DAS system can be used with single-modes and multimode fibers and it can be used for dynamic water injection profiling and optimization.
Analysis of Water Hammer Signatures for Fracture Diagnostics
Authors: Carey Michael A. , Mondal Somnath , Sharma Mukul M.
Published: September 2015

A sudden change in flow in a confined system results in the formation of a series of pressure pulses known as a water hammer. Pump shutdown or valve closure at the conclusion of a hydraulic fracture treatment frequently generates a water hammer, which sends a pressure pulse down the wellbore that interacts with the created fracture before returning towards the surface. The result is a pressure profile that consists of a series of oscillations that attenuate over time due to friction. Created hydraulic fractures have been shown to alter the period, amplitude, and duration of the water hammer signal. The goal of this study was to simulate the water hammer response of hydraulically fractured wells, and quantify how fractures affect the response.

Water hammer pressure signals were simulated in this study with a numerical model that combined the continuity and momentum equations for the wellbore with a hydraulic fracture represented by a circuit with a resistance, capacitance, and inertance (R, C, and I) connected in series. To test how each variable affected the water hammer signal, the R, C, and I variables were each individually altered through a range of values while all else was held constant. Furthermore, field data from several fractured wells were history matched with the numerical model by iteratively altering R, C, and I until an appropriate match was obtained.

Changes in the fracture resistance, capacitance, or inertance are shown to alter the simulated water hammer signature. Variations in capacitance alter the period of water hammer oscillations and the average pressure sustained by the water hammer. Variations in resistance affect the initial water hammer amplitude and the rate of oscillation decay. Variations in inertance affect the period of the water hammer. Field data from hydraulically fractured wells was successfully history matched, and R, C, and I values were obtained for each well. Fracture length, height, and width were calculated from derived expressions based on R, C, and I, and were in good agreement with other fracture parameter estimation methods.

The results from this work indicate that the water hammer signals at the conclusion of a hydraulic fracturing treatment are affected by the created hydraulic fractures. Thus, water hammer fracture diagnostics will yield important information about the created fracture such as the relative size (derived from the calculated length, width, height) and connectivity (indicated by the resistance value, R) to the wellbore.
Real-Time Monitoring and Diagnosis of Electrical Submersible Pump
Authors: Han Guoqing , Chen Mian , Zhang He , Ling Kegang
Published: September 2015

Electrical Submersible Pump (ESP) lift is extensively used in offshore production systems. Although real-time pump operating parameters and the production data are commonly available according to the recently developed digital energy technologies, the analysis of the acquired data is still insufficient to monitor, diagnose, interpret, and analyze reservoir performance, wellbore integrity, and ESP operating status and efficiency in a real-time manner. Further, the traditional ammeter card diagnosis cannot identify leakage of tubing, underperforming pump lifting, and low pump working efficiency.

This paper summarizes typical characteristics of different downhole malfunctions in ESP wells, provides a novel approach to detect those problems systematically and automatically. The developed management system incorporates real-time ESP current data and interpret ammeter card by neural network analysis, which has been trained through over 900 wells. We also derived the analytical solutions for wellhead pressure buildup analysis as a supplement to neural network analysis. Consequently, this model is able to detect downhole problems that cannot be identified by ammeter card. This diagnosis model also sets thresholds for key parameters, and alarm operation team through satellite in a timely manner. This model is a reliable supplementary to the traditional ammeter card diagnosis method, and the online utility provides complement flexibility to cooperate with field operations in real-time. The early-stage identification and resolution of ESP problems can lead to a great cost-saving and less maintenance requirements owing to this intelligent system. This workflow has been successful in field trials.
Experimental Study of Drop Size Distribution for Air-Oil Two-Phase Flow in Large Diameter Pipe
Authors: Gawas Kiran , Pereyra Eduardo , Sarica Cem
Published: September 2015

This paper presents the results of a study conducted to measure size distribution of liquid drops entrained in the gas phase, for air-oil two-phase flow. Experiments were conducted for the low-liquid loading horizontal flow in large diameter pipe indicative of wet gas transportation pipelines. The flow loop consisted of 0.015 m (6 in.) diameter and 56 m long horizontal pipe. A backlit high speed visualization system was developed to capture images of the entrained drops. The images were processed and analyzed to determine drop size distribution. Images were captured at three different locations along vertical axis of the pipe, and distribution of the entrained liquid drops at each location was analyzed. The changes in size distribution and average size of drops along the vertical axis were studied at different gas flow rates. Upper limit log normal (ULLN) distribution and log normal distribution were used to fit experimentally determined size distribution. Stratification of drops was observed and average drop size was found to decrease from bottom to top of the pipe. The spatial variation tended to decrease with increase in gas velocity. Experimentally determined drop sizes were greater than those predicted by available correlations for Sauter mean diameter (SMD), volume median diameter and maximum diameter. The error tended to increase from bottom to top of the pipe. The discrepancy could be because most of the available correlations are empirical based on data for air-water flow, which is a high-surface tension system, and commonly for vertical annular flow. Accurate estimation of size of entrained drops is necessary for prediction of their concentration distribution across the pipe cross-section and fraction of liquid entrained in the gas phase. This is required for prediction of pressure gradient and liquid holdup and evaluating flow assurance risks in condensate pipelines.
Leak-Off Test Model Combining Wellbore and Near-Wellbore Mechanical Behavior
Authors: Gandomkar A. , Fu J. , Gray K. E.
Published: September 2015

Considerable efforts to model leak-off test (LOT) and leak-off behaviors have been carried out in the past. Altun presented a method to estimate leak-off volume by dividing the pressurized system into four sub-systems: mud compression, casing expansion, fluid leakage, and borehole expansion (Altun 2001). The volume response from each sub-system is then combined to represent the total volume pumped during a LOT.

Most existing leak-off models do not account for mechanical behavior of cement and rock formations around the wellbore. While their compressibilities are small, the cement and rock formation volume changes can be significant. In this study, a mechanical expansion model has been developed, based on a linearly elastic, concentric cylinder theory developed by Norris (Norris 2003). The model is an extension of Lame' equations for multi cocentric cylinders and assumes the horizontal stresses on the system's boundary are applied equally in all directions, i.e., the horizontal, far-field stresses around the system are isotropic.

The resulting model simulates the compound radial displacements of casing, cement, and formation along the cased hole, based on pressures inside the wellbore and in the far-field stress region. The volume generated from concentric cylinder expansion is then combined with Altun's mud compression volume and fluid leakage volume to simulate the total volume pumped during a LOT. One use of the model is the estimation of minimum horizontal far field stress. Since the model consists of concentric cylinders, the pressure on the outside boundary can approximate the minimum horizontal far field stress, which in turn and related to overburden pressure. The pressure inside the most inner cylinder is calculated from known mud weight. With an initial estimation for the far field stress and iterative methods, the minimum horizontal stress can be estimated.

The developed models were then applied to field LOT data from the Gulf of Mexico. The results show that leak-off volume along the cased hole should be analyzed as a compound expansion of casing, cement, and formation. Since horizontal far field stresses in the GOM are almost equal (low anisotropy) (Salehi and Nygaard 2012), the Wider Windows LOT model simulates leak-off volume, leak-off behaviors, and far field stress.
Successful Testing of Single Gradient Subsea MudLift Drilling Technology in Deep Water Gulf of Mexico
Authors: Sharifur Rahman , Calvin Holt , David Dowell , Danilo Morales , Siri Davis
Published: September 2015

Subsea MudLift Drilling (SMD) technology is a form of Managed Pressure Drilling (MPD). Similar to other MPD systems the SMD technology offers early detection of influxes (kicks) and minimizes downhole losses to weak sub-surface formations. However, very significant and beneficial differences are built into the SMD system.

Two variations of Subsea MudLift Drilling techniques are currently being tested in deepwater Gulf of Mexico: SMD Dual gradient (SMD-D) technology also known as dual gradient drilling, andSMD Single gradient (SMD-S) technology also known as single gradient managed pressure drilling.

In deepwater drilling operations, the effect of annular friction pressure (AFP) often reduces the drilling window between pore pressure and fracture pressure. The SMD-S technique allows for the reduction of the dynamic bottom hole pressure by pumping off a portion of the AFP while drilling. Through greater management of the bottom hole pressure, this technology enables efficient navigation between the pore pressure and fracture gradient profile. As a result, tremendous value can be realized through reduction of non-productive time and the drilling cycle time. Further, the technology may enable drilling highly deviated extended reach wells in a deepwater environment, which can potentially increase total recovery with reduced well count.

The SMD-S system was successfully tested on one of Chevron’s Deepwater GOM exploration wells. This deployment was the penultimate step in an extensive testing and qualification process to ensure the equipment functioned in accordance with all required design conditions, and that the operational procedures allowed for delivering a well safely. In addition to training key operator personnel, rig contractor, and service company personnel, engagement of third party reviewers and regulatory agencies was critical throughout the process.

Lessons learned were recorded and corrective actions implemented throughout the process, from initial testing at the component level through the subsea deployment of the entire system. As these items are addressed and incorporated back into the equipment design, training, and operational procedures, a plan is in development to drill an entire well utilizing the SMD-S technology.

This paper will highlight the benefits of SMD-S technology, the execution of the most recent deployment and test results that are the final steps in moving towards continued managed pressure drilling operations in the deepwater GOM.
Architecture Characterization of Sandy Braided Fluvial Reservoir: A Case Study of P Oilfield (Neogene), Bohai Offshore, China
Authors: Zhongbo Xu , Kai Huang , Chunsheng Shen , Xianbo Luo , Bin He , Kai Kang , Yukun Chen , Xinrong He , Lin Li , Bowen Zhang , Jiaqi Liu , Guosong Lin , Xiaohong Yang
Published: September 2015

The architecture of sandy braided rivers, especially the mid-channel bars and the internal intercalations, plays a key role in the enhancement of remaining oil. Based on ancient outcrops, modern deposits and geological models, taken P oilfield as an example, this paper studies the different hierarchies of the internal architectural elements to describe the heterogeneity of sandy braided fluvial reservoir qualitatively and quantitatively, and proposes techniques to characterize the architecture of underground braided fluvial reservoirs. Based on the proposed distribution pattern and the related characterization techniques, the different controls of architecture elements on the distribution of remaining oil are analyzed: (1) sandy braided rivers have three filling patterns, dominated by sandy fillings. The mid-channel bars and braided channels are distributed in the pattern of wide bars and narrow channels, while the silting layers within mid-channel bars have dome-like and horizon-like distribution patterns; (2) the architectures are characterized from 5th to 3rd-order hierarchies successively under the principle of thickness control, scale constraint and multidimensional interaction. Single braided belts can be classified by three identification marks (the average width/thickness ratio is about 178, the width ratio of braided channels and mid-channel bars is about 1:3.8, and the width/length ratio of mid-channel bars is about 1:2.2); (3)Single-period silting layers are nearly horizontally distributed within mid-channel bars and multi-period ones are parallel with each other, generally 2-4 silting layers; (4)Reservoir architectural elements of different hierarchies exert different controls on the distribution of remaining oil. The intercalations control the remaining oil directly in the hierarchy of braided belts. In the hierarchy of mid-channel bars, semi-muddy filling channels have enriched in remaining oil due to relatively poor watered out degree as a result of disconnected sand bodies in the upper part with connected sand bodies in the lower part. Influenced by silting layers and petrophysical boundaries, the remaining oil within mid-channel bars is mainly distributed as “segment-like” enrichment at the top of vertical aggraded bodies under the silting layers and at the margin of poor water flooding. Overall, the research not only has good applications in the integral adjustment schemes of mature wells and development designs of news wells in oilfields, but also provides geological basis for well deployment of adjusting wells, especially for producing remaining oil in horizontal wells.
Effective Training Delivery Mechanism-A Successful Case Study
Authors: Al-Anezi Nayef Abdulla , Al-Daihani Eisa Hadi , Raza Syed Mohammad , Nandi Arun Kumar
Published: September 2015

Training and development is recognized as critical support function of the organization. It has greater impact on assets which are diverse depending on the delivery mechanism. Identifying the most effective training solution to enhance the human resource and eventually organizational capability is only one aspect of delivery mechanism. The main and very critical aspect of delivery mechanism which has two way impacts on the organization is the adequate tools and techniques adopted to implement the learning solutions.

Kuwait Oil Company has introduced a comprehensive integrated delivery mechanism ensuring the quality control at all stages; planning, implementation and evaluation. As a case study, this paper will present the mechanism of two learning solutions/ learning tools (Instructor led training course and on job training). A multidimensional assessment tool kit to determine the effectiveness of the Instructor led courses and on-job training has been established which is a systematic approach of delivery mechanism and that lead to Quality Assessment team to evaluate the effectiveness more accurately. Accordingly, key elements have been identified which indicate the training efficiency. The training efficiency is then checked with knowledge assessment (Gap Filled) with the aim to ensure accuracy. An equation for instructor led and on the job training has been evolved to determine the efficiency of the training delivery mechanism.

The present paper is focusing on effective training delivery mechanism adopted by Kuwait Oil Company for learning solutions ensuring various aspects i.e. meeting the training objective, cost effectiveness and quality control. Defining competencies, ensuring the alignment with business needs, assessing the current competency level of employees and developing action plans accordingly are the main examples of a systematic approach of capability development at planning stage. Such an approach will help the company to meet its strategic target.

To resolve the issue of capability development and the associated challenges, a long-term and genuine cultural change is required to create environments where knowledge sharing is expected and normalized. The solution needs to be driven from the top, with senior management making a visible commitment.
How Culture And Practice Workshops Can Help Developing The Safety Accountability Of Operational Staff
Authors: Kiehl Vincent , Amadeï Christophe , Pradié Emmanuel , Sibout Marie , Boj Claude , Watremez Xavier
Published: September 2015

TOTAL has conducted a global safety culture assessment in its Exploration & Production Affiliates. Further to this assessment, Culture and Practice workshops were organised in selected business units (currently in Total EP Angola) to develop the safety accountability of employees and to promote cooperation of teams.

On each selected site, one-hour sessions were organized each day over a two week period and were repeated three times. They were proposed to all employees, from the Production Operator up to the Site Manager. Each group had a maximum of eight people and ensured that all levels of site personnel were represented.

Two facilitators with multidisciplinary competencies led the workshops: an Occupational and Industrial Psychologist and a former Operational Manager. They gave a common basis to work on the safety culture. They encouraged interactive discussions to bring sense, when required, to the existing safety corporate messages, rules and procedures.

The workshops progressed in five successive stages: (1) Introduction; (2) Teams' request; (3) Highlights; (4) Taking ownership and accountability; (5) Debriefing.

The workshops focused on the meaning and the consistency of existing practices on safety rules and initiatives. Based on open discussions, the participants mentioned the topics on the safety culture important to them. The three main topics were: (1) Risk assessment and management; (2) Exemplarity of management; (3) Accountability of individuals.

The groups debated and proposed to change some working practices to improve the safety culture. At the end of the workshops, they debriefed their work to the Site Management and to Operational Directors, as to commit all the personnel on the proposed changes in practice.

These workshops held both onshore and offshore demonstrated a strong mobilisation towards safety. The dynamics created had a very positive impact on the all personnel behaviour. As a consequence, the Company is using this new and effective approach towards safer operations in Other Business Units.
Drilling the Undrillable: Atlanta Field Heavy Oil in Ultra Deep Water
Authors: Rausis Mauro G. , Pedroso Carlos A. , Salies Jaques B. , Libório Fernando , Moreira Marivaldo B. , Luz Pedro R. , Siqueira Jorge R. , de Oliveira Jessica F. , Marsili Marcelo D. , Nogueira Luiz M. , Heleno Ademir , Domingues Glauber T. , Aguiar Rogério
Published: September 2015

The development of heavy oil (14 API) in ultradeep waters (1550 m), in a reservoir 800m bellow mud line is a technological challenge all over the word. This paper will present the solutions applied successfully to drill, gravel and test two horizontals wells under these extreme conditions.

Atlanta field is a post-salt oil field located offshore Brazil, in the Santos Basin, 150 km south of Rio de Janeiro. The water depth has approximately 1550 m, the reservoir sits 800 meters bellow the mudline, has an unconsolidated sandstone with an average 38 % porosity with high permeability and a 14 API oil. This paper presents most of the challenges the operator had to overcome to drill, gravel and test two wells already with great success. Both wells have a casing program composed by 36″/16″/11 7/8″ and an horizontal section of 800m drilled in 9½″. Due to the 14 API oil the artificial lift method chosen was ESP (1500 HP) installed at an inclination of 75 degrees of the well. To install the pump the well profile was built with a slant section of 100 m with maximum DLS of 1 degree/100ft to avoid fatigue during the operation, but also a maximum dogleg of 5 degree/100 ft to avoid damages to the pumps while running into the wellbore. To be able to achieve the constrains imposed by the ESP, from mud line at 1550 m to the top of the reservoir at 2330 m the well profile design had to achieve a 43 inclination during the riserless drilling section of the well, the techniques applied are described in details in the paper. The next challenge was to drill the horizontal section with a very narrow margin from collapse to fracture of the well, all the procedures regarding drilling fluids and drilling techniques are presented. The 800m horizontal section was drilled in 9½″ to allow the use of 6 5/8″ premium screens to increase production. To guarantee a minimum content of sand in the produced oil with the objective of increasing the life of the ESP the well was gravel packed. Due to a small fracture gradient of the previous shoe 11 7/8″ the gravel was performed successfully with a special propant with very low weight, again the details are presented. The wells were tested with two different positions of the pump: one at the bottom of the well, and other at the sea level just above the BOP. The objectives of the test were to compare the performance of the reservoir with the pumps in two different positions, but also to study the flow assurance problems that may occur after programmed or non programmed stops of the future production system. All the results and main conclusions are presented.

The excellent results obtained from the drilling, gravel and testing of both wells, which are presented in this paper, confirms the potential of Santos basin’s Atlanta field.
Dynamic Multiphase Process Simulation as a Powerful Tool to Sustain Production: A Real Case Application
Authors: Riccio Gaetano , Di Sarra Andrea , Bianco Amalia , Dibello Francesco , Masi Silvia
Published: September 2015

The full potential of simulation has, to date, not been fully exploited for numerous reasons, including but not limited to lack of awareness of this computational approach. Nowadays, steady state simulators that model operating plant are used as the custom-made tools to predict global performances, even though they are not able to mimic ‘real’ process behaviour.

The work described herein introduces dynamic process plant models as an efficient way to simulate time-dependent variables, handling changeable ‘real-time’ operating conditions.

A stabilization unit was the object of an engineering study with the intent to sustain production, enhance energy efficiency and safety of operations through low-cost computational technology. The entire process plant was modelled and tuned with commercial simulator equipped with a dynamic suite. The latter requires equipment data and real geometry to simulate operating conditions upsets, feed or composition change in a transient way. Once the steady state model is matched, the switch to dynamic environment allows the user to model upset of input variables and to study system response. It guarantees to adapt the entire process in a new and more efficient configuration by optimization of the control system.

Steady state simulations are very fast and use continuous, time-interval based, steady-state approximations, requiring the least effort to set up and calibrate. Contrariwise, they are not able to simulate transient phenomena and control system responses, thus limiting simulation capabilities to provide representative conditions of the real plant behavior.

Considering that cost to benefit ratio is rapidly moving in favor of computerization, the implementation of dynamic simulations in process industries represents the best way to achieve complex targets. The presented case study demonstrates the strength of this approach and its influence on optimal monitoring and control of process plant performance.

Other benefits have been shown on real time optimization, including operational troubleshooting and field operating cost reductions.

‘Fine-tuning’ is the resume word of this work and represents the way to efficiently achieve complex targets, moving Oil & Gas toward applications that have otherwise been characterized only for petrochemical or complex plants.

Currently, the global energy world is facing even more complex scenarios, which technical engineers must address in order to confront the new challenges ahead.
Effects of Downhole Parameters on Horizontal Milling Applications
Authors: MacZura J. M. , Miller M. , Scuadroni N. , Daley D.
Published: September 2015

The increasing lateral lengths of wellbore and additional composite frac plugs (CFP) per well has created a need for a more efficient and aggressive post frac millout of plugs using coiled tubing (CT). Economic post job analysis has shown some advantages and drawbacks of using larger diameter coiled tubing and more robust tools, all while developing a better understanding of the impact to the operation. Several complexities exists downhole that are not well understood. Attempts to comprehend downhole conditions are limited by past experiences, pre-job software modeling, and post-job matching through the uses of surface parameter but not actual downhole data.

Monitoring downhole forces applied when performing post frac milling operations, through the use of a memory sub, gives a better understanding of forces that are actually transmitted from the tools to the CFP in the actual wellbore environment. Thru tubing tools selection is based on actual downhole data which translates to an overall increase in efficiency of the operation.

A closer look at the actual downhole parameters, when performing operations with larger diameter CT and extend reach tools, lead to findings that the weight on bit (WOB) applied to a plug in the lateral of a well can be as high as 15,000 lbf. This amount of force far exceeds what is applied at surface and what conventional software modeling shows. This also greatly surpasses the recommended WOB while drilling the CFP. Applying substantial downward force to the CFP results in movement of the plug prior to being completely milled up, which causes significant operational issues. These same forces that cause the aforementioned issues are necessary to aid in having consistent mill times throughout the operation, enough WOB to get CT to reach measure depth (MD), and produce an operation that is completed in a timely and economically sound manner.
Uncertainty and Risk Management Plans are Critical for Team Alignment and Better Decision Quality
Authors: Sawiris R. , Howes C. S. , Rodriguez J. A. , Foley W. L.
Published: September 2015

The Uncertainty Management Plan (UMP) and Risk Management Plan (RMP) processes are an integral component of Reservoir Management and Project Management at Chevron. The UMP and RMP are key to safely deliver and improve the movement of Resources to Reserves to Production (R2R2P) and the maturation of Organic Resource Opportunities (ORO) in a timely and economical manner.

The UMP helps project teams identify key uncertainties and develop robust work plans to resolve these uncertainties in order to improve decision quality and maximize value to the company. The RMP helps project teams identify key technical, mechanical and commercial risks, and develop appropriate mitigation and contingency plans for these risks. The RMP will also help the team identify and address process safety risks related to subsurface integrity issues. The UMP and RMP drive development plans, technology plans, surveillance plans, operating plans and resource loaded work plans. This is even more critical at the current low oil prices where many projects become economically challenged; we need to focus our efforts and resources to be decision driven and value driven.

We will compare and contrast the concepts of uncertainty and risk and present case studies of how the UMP and RMP were successfully used on a variety of assets. We will also discuss some of the pitfalls, lessons learned and best practices.
Treating Acid Mine Drainage for Use as Source Water: A Pilot Study
Authors: Beers T. , Heinrichs M. R. , Lane A. E. , Peterson R. K.
Published: September 2015

This project’s focus is to evaluate an Acid Mine Drainage (AMD) treatment technology for the purpose of providing treated mine drainage as an alternative source of water for hydraulic fracturing operations. The liquid-liquid extraction based technology allows the conversion of a previous environmental liability into an asset while reducing stress on potable water sources. This is a patented technology based on well understood and widely applied solvent extraction processes and has three distinct stages—water purification, metal recovery, and sulfate recovery—and produces three distinct and potentially useful byproducts. Water is able to be treated to reduce sulfate levels to less than 100 mg/L sulfate, and is able to remove most metals associated with mine drainage, including iron and aluminum, to low levels while maintaining high levels of water recovery.

Laboratory testing was conducted to optimize operational parameters of the technology specific to the AMD at the demonstration site located in Sarver, PA. Laboratory optimization of the process informs field testing as to the preferred operating configuration and parameters for the site specific water chemistry. System variables which would be difficult to test in the field, such as the number of extraction stages required or the optimal formulation of extractant were tested in the laboratory and system setpoints for the field pilot demonstration unit were identified. Following laboratory testing, a series of test runs were conducted in the field on a 100 gallon-per-minute pilot demonstration system. Field testing showed that the field system was able to remove sulfates to the levels required while operating under steady state conditions. Field results were correlated with laboratory results. Future field testing to be conducted in phase II of this project will include two distinct test campaigns to evaluate both the sulfate removal efficacy of the system as well as identify optimum economical operating conditions.
Scale Squeeze Fractured Reservoirs in the Bakken, North Dakota
Authors: Cook S. , Lu H. , Cutler J. , Haugen C. , Cenegy L. , McAfee C.
Published: September 2015

Scale inhibitor squeezes are common for scale prevention in conventional reservoirs, but similar applications into fractured reservoirs are unusual and the mechanism of inhibitor transport and retention is not fully understood. This paper discusses the selection and field application of a scale inhibitor for the Bakken, North Dakota fractured reservoirs. The Bakken development is a hydraulically fractured reservoir where calcium carbonate and iron carbonate scaling pose a threat to productivity, necessitating the deployment of preventative scale inhibitor treatments. The results of a comprehensive inhibitor testing program, including compatibility, formation damage studies, dynamic tube blocking and static adsorption testing are presented, providing an overview of the product selection criteria for the fractured reservoir. This paper demonstrates how production-, completion- and laboratory-derived data were used with treatment modeling software to enable the successful application of a scale squeeze into the Bakken formation. Complex Bakken completion orientations made the use of conventional modeling programs a challenge and a number of assumptions that were made are discussed in the paper. The final part of the paper reviews the squeezes performed on three Bakken wells, and discusses relative performance against the modeled treatment predictions. The scale inhibitor retention in the reservoir is documented, and possible mechanisms are discussed.
Searching for Energy Policy Alternatives
Authors: Blaskovich Frank
Published: September 2015

Energy policy resides in a socio-economic system that has many interconnected elements, feedback loops and delays that create behavior that is not easy to understand or manipulate to achieve desirable outcomes. This paper suggests a new approach to energy policies that tries to minimize stakeholder regret regardless of future surprises. We built a model to study the relationships among energy producers, government and society to develop taxation policies that would benefit all stakeholders fairly. Our focus was on oil, but is extendable to other forms of energy. The goals were to find policies that would encourage energy development, provide for the public's energy needs and enable government to safeguard society's well-being.

We used regret analysis to find the best stakeholder policies as well as compromises that would benefit all fairly. This defined the range of acceptable solutions. We then used regression trees, differential evolution and genetic programming to develop policy algorithms that worked regardless of the future behavior of policy drivers such as oil prices, oil reserves and well productivity for all stakeholders (energy providers, government and society).

Sound energy policy requires creative insights into how complex systems function. Traditional techniques that tend to focus on one or a few aspects of the problem rarely succeed for long and often can create more problems than they try to solve. Looking at policy levers individually did not work as well as considering all policy levers simultaneously. This resulted in a complex set of interrelated policies that achieved a much better result than would be achieved with other approaches. We found that the feedback loops in the model could either work together or be in conflict under different conditions. Understanding system behavior required techniques that focused as much on the structure (i.e., how key features interact) as on the individual components.

A key feature of the new model was that it considered the impact of and on society of policy decisions. This was an iterative process and the best policies changed as additional complexity was added to the system. We also compared our results to actual government policies to validate the benefits of our approach.
A Competency Framework for Petroleum Engineering University Graduates
Authors: Aggour T. , Donohue B. R. , Donohue D. A.
Published: September 2015

Academia has a long history of collaborating with the oil and gas industry to ensure that graduates are well prepared to succeed in the workplace and contribute to their new employers. Industry extensively utilizes competency models as part of a process to manage and assure a competent workforce. The first level of job titles represented by industry competency models usually defines positions with two to three years of experience, progressively building up to more experienced job titles. It is logical to extend this methodology backward into academia, representing the expectations of entry-level new hires. This paper describes an initiative that builds on previous efforts by developing a rigorous competency framework for petroleum engineering graduates that covers the expected technical and behavioral competencies for new graduates at a high level of detail. The resulting framework has measurable competencies and can be utilized to great benefit by all stakeholders involved in the industry.

Academic programs can utilize the competency framework as a reference to influence curricular decisions and assessment protocols, helping to more effectively prepare graduates for their future roles and document the quality of their graduates.

Students will have a clear understanding of the expectations of them upon entering the workforce and have an opportunity to identify and remedy any gaps during their studies to improve their employment prospects upon graduation.

Potential employers and recruiters will now have a valuable new quantitative screening tool that can be used to compare the technical qualifications of graduating applicants and help match them to roles best suited to their technical competencies.
Next-Generation Boron-Crosslinked Fracturing Fluids: Breaking the Lower Limits on Polymer Loadings
Authors: Holtsclaw Jeremy , Montenegro-Galindo G. Rocio , Chopade Prashant
Published: September 2015

Hydraulic fracturing is a robust stimulation technique that has been employed for more than 60 years to help increase the recovery rate of hydrocarbons from reservoirs. Hydraulic fracturing fluids are key components of the process. Significant efforts have been made to refine the fluids and advance new technology to help improve the economics, efficiency, and safety of the systems. Specifically, the pursuit of fluids that provide reliable and consistent performance while using lower concentrations of polymer, usually guar or a guar derivative, has been a recurrent point of emphasis in fracturing fluid advancement. There are many advantages of using lower polymer concentrations, including lower costs, improved logistics, and introducing less polymer with its associated residues into the fracture, among others.

This paper presents a new fracturing fluid that combines a next-generation boron crosslinker with a new hydroxypropyl guar (HPG) to be crosslinked with 40 to 60% less polymer than used in conventional borate-crosslinked fluids. For this fluid, HPG loadings in the range of 8 to 12 lbm/1,000 gal were used to produce boron-crosslinked stimulation fluids stable up to 200°F. Fluid viscosity testing showed stable fracturing fluids with controlled breaking profiles at temperatures up to 180°F. Dynamic proppant suspension testing indicated that the new fracturing fluid exhibited proppant transport equal to or better than conventional borate fluids. Regained permeability testing using Berea sandstone cores exceeded 75% at 160°F, 85% at 180°F, and 95% at 200°F. Additionally, excellent fluid cleanup was measured by retained proppant pack conductivity with 2 lbm/ft2 20/40-mesh lightweight ceramic proppant.

This new boron-crosslinked fluid retains the “rehealable” property and flexibility of conventional borate-crosslinked fluids; however, the polymer is crosslinked at or near the minimum concentration at which the polymer chains can entangle (and are capable of crosslinking), which is an improvement compared to conventional borate-fluids. This concentration is known as the critical overlap concentration, c*, of the polymer. The use of the new crosslinking technology coupled with the new HPG allows for a two-fold advantage in terms of residue reduction. The derivatized polymer requires additional processing, yielding a cleaner polymer with less residue, and the lower polymer dosage results in a further reduction of residue compared to conventional fluids.