bluuebunny/crossref_metadata_2025_split 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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.