bluuebunny/crossref_metadata_2025 huggingface dataset:
A Project Mode in Developing Oil and Gas on Artificial Islands: Cases Study of EPC, Batch Operation and Extended Reach Drilling
Authors: Lyu Yixiang
Published: November 2017

Developing the offshore oil and gas resources on an artificial island is relatively economical compared to a drilling platform, thus it is adopted widely by oil companies. Nevertheless, it still has higher construction, maintenance and development costs than onshore field developments as well as added technical issues. To overcome those challenges, a proper contract, management and technical proposal would benefit artificial islands projects, especially with current low oil price circumstances.

To establish a proper project mode for reservoir development on the artificial islands, this paper describes cases in 3 different aspects: first of all, the principal activities in the engineering, procurement, and construction (EPC) contract of Garraf drilling project in Iraq are introduced, including the complete service system, organization structure and human resources, health, safety and environment (HSE) management, cost and risk control, project period, research and technical support. After that, the batch operations in Weiyuan shale gas project in China are presented to demonstrate the production process. Finally, the experience of technical optimization of extended reach drilling (ERD) in Cuba is shared.
Twisting Slip and Rotation of UAE Fault System
Authors: Obaid Khalid , Noufal Abdelwahab , Mahgoub Mohamed
Published: November 2017

Abu Dhabi fields are influenced by strike-slip and their damage zones as a main tectonic regime. A damage zone is the deformed volume of rocks around a fault surface that results from the initiation, propagation, interaction, and build-up of slip along fault segments. These damages zones impacted the distribution of the traps, migration pathways and increasing the drilling risks. Slippage and rotation along the fault segments in Abu Dhabi fields increases the damage zones widths around the fault segments. This paper presents a detailed description of the kinematics and dynamics of rotated damage zones in the strike-slip faults of Abu Dhabi fields.

The factors that are controlling the damage zones around faults are mainly the rock type, relation between bedding and fault plane and stress tensors. This paper, however, focuses on the structures within the damage zones as they are influencing the trapping mechanism, the drilling hazards and how the rotation increases these. In addition, the structures formed at the fault tips are also considered, especially for the initiation and propagation of the fractures. Field examples and outcrop analogues of damage zones around strike-slip faults are presented. This study is integration between seismic, cores, logs, and outcrops.

During the Late Cretaceous the kinematics of Abu Dhabi fault system changed to transtensional and accommodated a major component of left-lateral strike-slip motion with a SE-NW compressional component. The final phase occurred by the Miocene time, where the stress tensor is changed to NE-SW compression, which rotated the blocks. During this deformation, the blocks were dissected into a series of large-scale blocks bounded by NW-trending left-lateral strike-slip faults which merge into a NE–SW fault system that forms the main structures in Abu Dhabi. Field studies on the mountains exposures data from the fault bound subsurface blocks indicate 10°–15° of post-Early Miocene anticlockwise rotation with substantial latitudinal motion.

The decrease/increase of stresses along the fault segments in the overlapping/linkage zones and at the fault tips under differential confining pressures affecting the rocks behavior and understanding of these will greatly avoid drilling dry holes and reduce the drilling risks.
Seismic Characteristics, Identification and Comparison of Strike Slip Fault Systems in Onshore/Shallow Marine Fields in Abu Dhabi, UAE
Authors: Aamir Muhammad , Ahmad Mula Nur , Noufal Dr. Abdelwahab
Published: November 2017

In Abu Dhabi fields, strike slip faults can be originated from deep seated basement and/or reactivated salt related faults in a wrench tectonic regime. This paper outlines the identification of strike slip faults using 3D seismic imaging and describes the characteristics, orientations, spacing of the fault zones and the characterization of fault corridors through horizontal wells. Finally comparing similarities and contrast in the faults systems between different fields at the seismic scale.

The structural development and deformation mechanics associated with the Late Cretaceous tectonic phase represent the key factors of hydrocarbon accumulation in Abu Dhabi, where strike slip fault system that forms structural traps with several discoveries have been made.

3D seismic analysis has been performed on multiple 3D seismic cubes, and structure sensitive seismic attributes at different stratigraphic levels has been derived to better understand structural characterization and the geometry of Strike Slip systems. The main NW-SE fault system consists of a complex series of sub-parallel faults that connect via transfers, relay ramps or accommodation zones. Seismic images shows that these zones are associated with micro faults, fractures and folded closures resulting from the development of positive and negative flower structure.

These deep-seated faulting generally drives strike-slip tectonics happened when basement faults are reactivated a zone of rotational bulk strain develops in the overburden. The strain is accommodated by a variety of en-échelon structures including Riedel shears, normal and thrusts faults and folds. However, in deep seated detached salt related tectonics, a symmetric, conjugate pair of strike-slip faults will develop accommodating rotational bulk strain
Long Term Downhole Wet-connector Technology for Separate Injection Well - A Case Study in Changqing Oil Field
Authors: Yang L. , Mu L. , Lu H. , Huang W. , Yao B. , Ju Y. , Wang J. , Yu J. , Hu G. , Wang Z. , Wang S. , Wang W. , Zhang S. , Lu X. , Sui L.
Published: November 2017

Drill pipe conveying wet-connector horizontal well logging technology is a more mature logging technology. It could be used in all kinds of well loggings, even in highly-deviated wells and horizontalwell, as its downhole joint is connected to the bottom of the drill, using cables to carry heavier and the joint under pump. The two joint complete electrical and mechanical connections, located in themud, cannot meet the need of field test, since it generally lasts less than 15 days. Therefore, longterm downhole Wet-connector technology for separate injection well is proposed, basing on wet-connector horizontal well test technology. This technology mainly consists of the lower docking and upper docking. Specifically, the lower joint is connected to the top of tool string after completion. The upper one joins up on the lower joint by cables from wellhead with help of gravity. Five flow holes of20mm diameter are assembly designed on the lower joint which unlocking mechanism stress is 1.2-2 t approximately. It achieves long-term stability, communications and power supply after docking and normal water injection consequently.

Changqing oil field application results show that the wet-connector has several advantages such ashigh success rate, repeatable docking and maintenance. Its various technical indexes could meet the requirements of power, communication and wells backwashing. This proposed technique is an effective method of dynamical real-time monitor and downhole control for seperate injection well in low permeable oilfield.
Early Gas Leak Detection EGLD
Authors: Baque Marc
Published: November 2017

One of prerequisite of any detection system is to get preliminary data from the risk analysis to estimate the safety, the socioeconomic and environmental impacts of a loss of containment. From this prerequisite it will be possible to consider a strategy for an early detection of a loss of containment, and to choose a particular method or technology.

Under this aspect, a leak detection system permits to set up a means of risk management: the earlier the leak is detected, the faster the pipeline operator can deploy countermeasures of the emergency plan.

Methods of early detection belong, broadly speaking, to two main families: "direct" methods based on the detection or the "direct" observation of the fluid after the containment loss;"indirect" or "deductive" which use the evolution of the measured pipeline operating data to deduct the probability of the loss of containment.

Fiber optic is considered as one of the most promising "direct" leak detection technologies. The fiber core normally used for telecommunication purposes can be converted as a sensor with the principle of light backscattering within the fiber.

Distributed temperature or acoustic profiles can be obtained with the analysis in real time of the light backscattered when sending a light pulse in the fiber.
Electromagnetic Corrosion Logs, Insights from Yard Test
Authors: Macki Ali Al , Salmi Albashir Al , Duggan Timothy , Delgado Eduardo , Kechichian Jackie , Busaidi Hamood Al , Azri Nasser Al
Published: November 2017

Well integrity is one of the highest operational risks for E&P companies across the industry. As such, well integrity concerns are high priority for operational excellence. Electromagnetic Corrosion Logs have been more frequently acquired as Cased-hole logging services enabling the quantification of multi-barrier well integrity. Due to ease of data acquisition through logging operations and the ability to model remaining metal thickness per-barrier from acquired surveys, demand for Electromagnetic Corrosion Logs has been sharply growing across the industry. Electromagnetic Corrosion Logs can compliment conventional integrity tests and can be used for well integrity compliance where business-critical decisions are accordingly made.

Electromagnetic corrosion logs are run more frequently across assets to investigate time-lapse per-barrier integrity status for multi-barrier systems (multiple concentric tubulars). Degradation in barrier integrity in operating wells present integrity risks. Harsh operating environments during production/injection, sour environments, life-time wear and tear, and shallow aquifers all affect wellbore integrity in the form of internal and external metal loss. Electromagnetic Corrosion Logs are currently reported to be capable of quantifying total remaining metal per-casing (separately) up to three barriers.

In 2016, a yard test was conducted in Oman to assess the limitations of different Electromagnetic corrosion tools. The test consisted of multi-barrier concentric oil-field tubulars of different sizing and set-up. Four tubular set-ups (simulating routine well completions) were constructed with man-made "corrosion" features to assess raw, processed and interpreted Electromagnetic Corrosion logs. The man-made features included defects of various shapes and configurations distributed axially and longitudinally as well as machined thickness-loss areas with precise thresholds. Multiple service providers with different tools and configurations were requested to acquire corrosion logs through the yard test "completions."

This paper investigates Electromagnetic Corrosion Log technology. It illustrates the physics, practice, and applied technology scope of Electromagnetic Corrosion Logs gathered from the yard test and multiple surveys in Petroleum Development of Oman (PDO). The outcome is improved awareness of operational windows, tool resolution and sensitivities, detection capability, data QC and analysis, processing, and modeled thickness outputs. Some discussion is made around the limitation of Electromagnetic Corrosion Logs and the uncertainty in thickness estimation, and recommendations for this technology's scope for application.
Optimal Equivalent Liquid Rate ELR in Managed Pressure Drilling
Authors: Huang Xiaoqian Christina , Samuel Robello , Morales Gabriela , Parak Mahdi
Published: November 2017

One of the most important factors when designing an aerated-fluid drilling operation is the volume of injected gas and liquid necessary for the downhole mud motor to achieve managed pressure drilling (MPD) conditions.

This paper discusses a new method for calculating the equivalent liquid rate (ELR) of the gas/liquid mixture. ELR can be equally treated as the liquid volume to measure mud motor performance and can also be used to refine the permissible MPD operational window.

During aerated-fluid drilling, gas/liquid are mixed to form one complex flow regime along the wellbore. To model its flow rheology and mechanisms, both foam and multiphase flow models are used. ELR is calculated by using the surface gas injection rate (GIR)/liquid injection rate (LIR), drillstring configuration, wellbore trajectory, and wellbore geothermal allocation. This calculation also considers tool joint effects and formation influx from downhole and parasite string injection.

This paper also describes the impact of ELR to form the MPD operational window by considering GIR/LIR, minimum/maximum ELR, bottomhole pressure (BHP), and annulus flow velocity. Sensitivity analysis is performed for various combinations of GIRs/LIRs. Similar ELR value trending is observed in foam and multiphase flow models for both vertical and deviated wells. Increasing ELR is not always the goal because BHP should be controlled within reasonable ranges during MPD. To ensure operational constraints at the bottom hole, a set of ELRs is calculated from a few combinations of surface GIRs/LIRs. Refined by the target BHP and the desirable hole cleaning capability, the permissible managed drilling operation window can be achieved and visualized.

Drilling engineers can calibrate surface GIRs/LIRs to achieve maximum mud motor performance. Conversely, with the fixed GIRs/LIRs, to maintain the desirable BHP and hole cleaning, drilling engineers can select the proper mud motors for use.

The calculated ELR in this method is not only variable for evaluating mud motor performance, but it is also novel to combine it with other important operational factors to help manage downhole pressure and meet hole cleaning requirements.
Optimization of the Operation Time Required for Data Gathering Requirement in Extended-Reach Drilling Well by the Use of Open Hole Tractor in the United Arab Emirates
Authors: Toki Takahiro , Benygzer Mhammed , Wahedi Khalid Ahmed , Anurag Atul Kumar , Singh Rudrap Pratap , Sayed Mohamed I , Ruzhnikov Alexey , Cocagne Michael Jason
Published: November 2017

Gathering of wireline data in Extended Reach Drilling (ERD) wells is still not a standard process, complicated even more by inclination and step out. This paper presents a case study of recording logs conveyed using an open hole tractor in a highly deviated section. The challenge was made more difficult because Water Based Mud (WBM) was required to allow the full suite of planned logs. The operation time that can be saved is up to four days.

The 8.5 in. pilot hole was designed based on the target and the sidetrack points for the mother hole. The inclination of the pilot hole was 63° and the wireline accessibility simulation based on offset friction factor showed that the open hole was not 100% accessible with Wireline Conveyed Logging (WCL) string. Therefore, an open hole tractor was selected to reach the required point. To minimize the risks for the logging operation, a six blade Polycrystalline Diamond Compact (PDC) bit, Rotary Steerable System (RSS) and Logging While Drilling (LWD) were used in the pilot hole to make a smooth trajectory and confirm wellbore conditions.

The logging operations were conducted smoothly and safely. It was observed that the actual results matched very well simulations, and the open hole tractor was required to convey the tools to the Total Depth (TD). The total tractoring length was 16,000 ft over the four runs, and there were no issues observed during the tractoring which confirms that the steps taken while drilling the section were correct and approximately four days of operation were saved by means of the open hole tractor as compared to Pipe-Conveyed Logging (PCL) operation. In addition, the mother hole length also was minimized to get proper sidetrack point from the optimized pilot hole trajectory and the potential total saving time would be more than seven days.

This paper also describes the optimization of well trajectories for pilot hole and mother hole and the gap related to planning from drilling and logging points of view, with aim to ensure 100% data gathering. The use of an open hole tractor for long interval in highly deviated well is the first time in the United Arab Emirates (UAE) and WBM conditions are non-standard operations which require significant amount of preparation during execution.
Improved Recovery of Carbonate Reservoir by Optimizing Acidizing Strategy; Coupled Wellbore, Reservoir, and Geomechanical Analysis
Authors: Safari Reza , Smith Clayton , Fragachan Francisco
Published: November 2017

One of the sources of damage in stimulated carbonate rock is the loss of near wellbore formation compressive strength which may results in casing collapse under extreme conditions. Field studies have shown that the failure of acidized rock may cause damage and thereby negatively impact production. In this work, an integrated analysis workflow is presented to simulate acid placement in carbonate reservoirs and model stimulated rock behavior during the productive lifetime of the well. The workflow is utilized to design a unique approach to horizontal wellbore acidizing and optimize the strategy to maximize hydrocarbon recovery.

The presented workflow is based on the interaction between the distributions of reactive fluid along a wellbore, a two scale continuum model to simulate porosity evolution during stimulation, and stimulated rock performance during production time. The model first simulates stimulation fluid movement in the wellbore and couples it with transient reservoir flow. The primary analysis provides the distribution of reactive fluid along the well. The rock dissolution at each section of reservoir is then analyzed by continuum two-scale model (pore-scale and Darcy scale). This analysis presents porosity evolution at different locations along the well and at different radial distance from the wellbore center. Then, the developed geomechanical engine simulates the weakened rock under the in-situ stresses and bottom-hole pressure and predicts any possible compressional or shear failure. The effect of rock failure is then considered on the production prediction.

The workflow is best used to analyze and optimize acid stimulation for a horizontal well. The analysis results show that the induced wormholes are stable and open since reservoir depletion increases the effective mean stress. At the elevated mean effective stress, wormholes or pores start to collapse and the failure extended away from near wellbore region and neutralized the stimulation effects. Since in the acid treated zone the rock is softened, the stress concentration around the wellbore might extended more into the reservoir. Analyzing this phenomenon showed that at a certain level of lowered stress concentration extension, in other words at certain strength and volume of acid, the wormhole can be stable and open during expected production time. Furthermore, the coupled analysis also demonstrates that at specific environment, the wormholes penetrated further into the rock, longer than possible

induced failure. The workflow can be used to determine how weak or strong the acid should be at specific environmental condition to have longer life for the induced wormholes and hence extra hydrocarbon recovery.
Flow Assurance during Gas Hydrate Production: Hydrate Regeneration Behavior and Blockage Risk Analysis in Wellbore
Authors: Deng Zhiming , Wang Zhiyuan , Zhao Yang , Guo Yanli , Zhang Jianbo , Sun Baojiang
Published: November 2017

Natural gas hydrate is a potential resource to meet the ever-increasing energy demand. Yet wellbore/pipeline blockage due to hydrate regeneration poses serious safety hazards during gas hydrate production. In order to estimate and effectively manage the blockage risk, we studied the hydrate regeneration behavior in wellbore during hydrate production. A method is developed to predict where gas hydrates regenerate (i.e. the hydrate regeneration region, HRGR) in the wellbore. The HRGRs with different production methods were studied. The results indicate that hydrates regenerate in wellbore. The hydrates can deposit onto the wall of the production tubing and form a growing solid layer, which narrows the tubing and even reults in complete blockage. The simulation work indicates that there tends to be a rather large HRGR in the production tubing regardless what production methods are adopted. The blockage risk is usually much higher in the region where a higher subcooling is encountered. This region is the high blockage risk region (HBRR). For the depressurization method, the HRGR shrinks as the depressurization amplitude increases. Accordingly, the HBRR and most vulnerable site become shallower. Therefore, the blockage risk is reduced. Similar trend is found as the thermal/chemical injection methods are used. However, for thermal injection and chemical injection, there are no significant change in the HBRRs and the most vulnerable sites. Only an unnoticeable slight upward trend is found for the thermal injection cases.
Reducing the Impact of Experience Gap and Increasing Service Delivery by Automating the Coiled Tubing Intervention
Authors: Aitken Bill , Micheli Rodrigo , Ramsey Tim , Dobkins Ken
Published: November 2017

The current coiled tubing (CT) industry as know is changing as a major service experience shift is being experienced; the generational crew-change is ongoing; the net result is a reliance on a smaller pool of qualified personnel. From a historical root-cause analysis across a variety of industries, we can contribute the human factor to more than 50% of Health, Safety and Environmental (HSE) and service delivery incidents. The solution presented in this paper highlights mitigating this potential risk by introducing several degrees of automation into CT interventions.

The foundation of the human-centered automation approach revolves around a software suite that incorporates pre-job modelling, real-time operational feedback, and active control of surface equipment during CT interventions. This approach updates operational parameters, to enhance safety and efficiency, and to increase the certainty of success.

This paper describes the process of bringing together the pre-job simulation with well intervention operating limits and real-time data acquisition, resulting in an automated programmable logic controllers (PLC) driven intervention that can intervene if/when deviations from job design occur. Five case histories are reviewed, and the benefits confirmed during field operations are presented. These findings outline the versatility of the automated system, resulting in the predictability of successful operations for operators.
Creation of a New Light Weight Grating
Authors: Tan Bugs Yeow
Published: November 2017

LIGHT WEIGHT AND ANTI SLIP GRATING PANEL

The invention of the light weight and anti-slip grating panel is an improved product that has significant advantages over common steel grating. Beside the many features found on the new grating, there are four major outstanding advantages over common steel grating. 1) The unique design of the new grating that is lighter by approximately 35% in weight. This is made possible with the creation of a hollow load bearing bar. The new grating being lighter in weight could also potentially reduce the overall weight of the main building structure. 2) Even though the load bearing bar is hollow but the overall integrity of the new grating panel is stronger. The new design can take approximately 12% more loads. 3) It takes a lot lesser raw material to manufacture the new grating panel. Thus, the finish product is priced competitively. This cost benefit will assist the consumer greatly in the overall project cost management. 4) The embossed rings found on the new grating provide a true anti-slip function. This safety feature aims to reduce the number of accident that occurs at workplace especially on oily working surface and stair treads.
Surfactants Impact on CO2 Sequestration for Enhanced Gas Recovery and in Depleted Carbonate Reservoirs
Authors: Eliebid Mohammed , Mahmoud Mohamed , Shawabkeh Reyad , Elkatatny Salaheldin
Published: November 2017

Indiana limestone cores were crushed and sieved to particle size of 125-250 microns, half of the sample was kept pure and the remaining has been treated with NaCl brine containing 0.1% (VES) viscoelastic surfactant to study the effect of surfactant on CO2 and CH4 adsorption. The carbonate rock was characterized using X-ray diffraction to determine the crystallinity. The adsorption measurement has been conducted at 50, 100 and 150°C and to 45 bars maximum pressure. At 50°C, adsorption uptake of CH4 and CO2 for untreated samples was higher than VES treated samples. However, at 100 and 150°C Both CH4 and CO2 adsorption capacities of untreated limestone was considerably lower than VES treated limestone. Thermodynamic studies indicate that adsorption on untreated samples was exothermic with ΔHads of -16.7 and -13.5 KJ/mol for CH4 and CO2 respectively and spontaneous adsorption at 50°C. In contrast, adsorption of CH4 and CO2 is endothermic with corresponding ΔHads of 60.1 and 36.2 KJ/mol and spontaneous at high temperatures. through all measurements CO2 adsorption was three times CH4 adsorption uptake due to high affinity between CO2 and calcite. Adsorption isotherms fitting shows that Freundlich isotherm is the best model to represent the adsorption behavior for all conducted experiments at all temperatures with lowest sum of squared errors (SSE) and highest R2. These results suggest that previously treated carbonate reservoirs that has mid-high temperatures has great adsorption potential for CO2 and CH4 making them an excellent candidate for CO2 sequestration.
Validation of a Workflow for Digitally Measuring Relative Permeability
Authors: Jerauld Gary R. , Fredrich Joanne , Lane Nathan , Sheng Qiang , Crouse Bernd , Freed David M. , Fager Andrew , Xu Rui
Published: November 2017

This paper provides a validation of a Digital Rocks workflow for computing relative permeability from micro-CT images of rock using Lattice Boltzmann simulation. The workflow has the potential to dramatically reduce the time and cost of measuring relative permeability by experimental techniques. Additionally, this workflow utilizes smaller volumes of rock than traditional laboratory techniques enabling the possibility of using side-wall cores and a further reduction in costs by avoiding costly coring operations.

The approach taken is to construct computational grids from segmented micro-CT images to define the pore space available for fluid flow, to run two-phase Lattice Boltzmann simulations, and derive relative permeability from the computed flow fields. Strategies for simulating both steady-state method and unsteady-state method relative permeability protocols are discussed. Five distinct stages of validation are described beginning with idealized 2-phase benchmark studies, progressing to physical micromodel experiments with a range of wettabilities, physical flow experiments in 3D grain packs with differing wettabilities, trapped gas measurement on sandstones with demonstrated dependence of trapped gas on pore structure, and finally corefloods on reservoir rocks.

The simulations quantitatively reproduce the displacement fronts and residual fluids distributions seen in physical experiments, and observed relative permeability behavior in coreflood experiments. Simulations of 2½-D micromodels reproduce the experimentally observed invading water front shape along with quantitatively matching residual oil saturation for the full range of wettabilities modelled; from water-wet to oil-wet. Importantly, simulations accurately capture the enhanced sensitivity of residual oil to intermediate wettability exhibited in the micromodel experiments. Residual oil trends for a range of 3D sandpacks of controlled wettability are predicted by simulation. The dependence of trapped gas on pore structure for Fontainebleau sandstone is reproduced quantitatively. And finally, simulations of relative permeability for reservoir rock for a range of plausible wettabilities are shown to be consistent with the results of laboratory measured relative permeability for reservoir rock from the same plug.
Preventing Failures In LDPE Plants Caused By Vibrations And Pulsations Of Reciprocating Compressors
Authors: Carcasci Cosimo , Sacco Marco
Published: November 2017

One of the main causes of damages and failures in industrial plants is the vibrations of related equipment; reciprocating compressors are particularly subject to vibration-related phenomena due to the operating nature of its moving part: alternating forces and pressure pulsations are in fact direct and inevitable consequences of their behaviour.

Particular care must be paid, during the design stage, regarding the interaction between the compressor and the plant as a whole to avoid that vibration problems may also arise after a machine has been installed.

The paper will describe a case that occurred in a polyethylene plant, where high piping vibrations resulted in ruptures, welding failures and hazardous gas leakages.

After a detailed root cause analysis of the failures, new more effective supports were studied and the exact positioning of the supports was decided, based on the results of a dynamic forced-response FEM analysis. The vibration measurements were used to locate the problems but also to tune the model, and subsequently to identify the key points where a stiffer structure could have been more effective. Consequently, many of the existing supports were reinforced and additional supports were added, with high damping fabric pads between the supports and the piping, in order to further reduce the impact of the vibration. Finally, also the cooler structure and foundations were reinforced.
Unique Cost Saving Solution Applied in Tight Gas Field in Sultanate of Oman to Mitigate Corrosion and Well Integrity Damage
Authors: Abdul-Majid Imran , Ayotunde Ajayi , Shihab Balushi , Abdullah Shuely , Blessing Oguni
Published: November 2017

This paper demonstrates an application of failure prediction and a cost effective solution to integrity problems of safety critical elements in wells in a high pressure, high temperature (HP/HT) gas field. Lekhwair field is a gas development in Northern part of the Sultanate of Oman producing approximately 2.8 MMSM3/D from the Upper Mafraq (UM) formation and Lower Mafraq (LM) formation. The LM formation has CO2 content in the range of 2-5 vol% which requires all the Lekhwair wells producing from this formation to be completed with stainless steel (FF) x-mas tree and tubing hangers.

At the onset of field exploration and appraisal, some wells in Lekhwair field were completed with carbon steel (DD) x-mas trees and tubing hanger which is incompatible with the CO2 component of the formation fluid. This has led to severe corrosion in some of wells. Consequently, a x-mas tree retrieval and inspection campaign confirmed the metal loss rate was standing at ~ 5mm/year.

To predict the meantime to failure of the DD tubing hanger and the x-mas tree, a robust stress analysis model was built to determine failure prognosis for the tubing hanger. The model was calibrated with actual data by integrating the measured metal loss observed on the existing x-mas tree after retrieval. This process has been embedded as part of reliability and failure analysis modelling for wells with DD x-mas trees and tubing hangers.

The outcome of the failure modelling showed that the tubing hangers would fail within 3 years if the hanger is consistently flow-wetted. This was used as a basis to develop a well integrity management plan and remediation solution for the Lekhwair wells with DD tubing hangers. To remediate the problem, the conventional solution applied in the industry is to execute a work-over to pull the existing tubing hanger and recomplete the well using the rig at a cost of 2 MMUSD/well with a 50% probability of success. This innovative new solution was devised by the team to execute an intervention using a slick-line unit and installing a through-tubing straddle across the existing tubing hanger to isolate it. This effectively prevents the tubing hanger from being flow-wetted and stops the tubing hanger from further corrosion. The solution has been deployed in the Lekhwair wells, and has been proven to lead to a cost and time saving in excess of 1.5 MMUSD/well and 10 days rig time, respectively.
Applicability of Managed Pressure Drilling MPD in a High Sulfur Content Fractured Reservoir
Authors: Safipour M. J. , Mavaddat Y. , Mavaddat M. , A'Rabi M. , Kadkhodaei N. , Abdollahi A. , Behbahani S. M.
Published: November 2017

Objectives/Scope: In this study, Managed Pressure Drilling (MPD) is investigated in a naturally fractured Iranian oil field as a tool to mitigate under balanced drilling hazards due to its high Sulfur content; and fluid losses and other problems that are inherent to conventional over balanced drilling.

Methods, Procedures, Process: MPD was identified, planed, and applied in an already drilled well, as an alternative technology, to calculate the increase in its rate of penetration (ROP). The calculations were made by Schulumberger Drilling Office package and quality checked by using Signa ERDS software. The software simulates drilling fluid dynamics to investigate application of drillind hydraulics to better chose the optimum drilling technique. Well drilling fluid properties, bottom-hole assembly, casing/completion design and rock formation properties are implemented as an input to the software to start calculations.

Results, Observations, Conclusions: The subject of this study was drilled in south west of Iran. Drilling experiences in this area identified the rock formation as a brittle, highly fractured, which negatively impacts drilling time and cost. Also, in certain instances, elevated mud weights are required to deal with high-pressure high sulfur content gas and/or water flows. Calculation shows that in shallow depths (0-470.8 ft, dd) due to low pore pressure, drilling mud is in balance and within pressure window. At deeper depths (470.8-7211.3 ft, dd) drilling is MPD and increase in mud pressure is required. At (7211.3-9530.8 ft, dd) depths, sharp changes in reservoir pore-pressure cause different increases in mud pressure (from 90 to 600 psi). At deeper depths (9530.8-13154.5 ft, dd) an increase in mud pressure may cause formation fracture, so it is suggested to continue overbalance drilling or separate the well bore by casing. If the formation is separated in previous section, drilling from 9530.8 to 13154.5 ft, dd, pressure management can be continued with an increase in applied back pressure in order to stop toxic gas hazards. At deeper depths (more than 13154.5 ft) according to high depth and dramatic pressure increase, it is suggested to continue MPD to prevent formation damage or induced fracturing and also prevent H2S influxes into annulus.

Novel/Additive Information: Tts the first time to apply MPD technique in a drilling well design in this filed as a solution to challenging drilling conditions like narrow pressure window, Toxic gas hazards, sever mud loss problems, differential stocking and blow out risks. Such results may result in a significant improvement in drilling economics.
Seismic Reservoir Characterisation for Horizontal Well Planning: A Field Case Study of an Unconventional Upper Jurassic Reservoir Onshore UAE
Authors: Caeiro Maria Helena , Al Kobaisi Abdulla , Neves Fernando
Published: November 2017

Seismic data offer valuable spatial information that contributes to the development strategy, such as drilling decisions and well planning. Inverting 3D seismic reflectivity data to impedance unlocks the potential of using seismic data to estimate the lateral variability and to predict reservoir geomechanical behaviour. The geomechanical model contributes for the evaluation of wellbore stability, frackability and drilling direction. The objective of this work is to illustrate the use of seismic derived models for reservoir and geomechanical properties, such as total porosity, total organic carbon (TOC) and rock rigidity. These properties are instrumental to characterize tight reservoirs and useful tools for defining a horizontal well trajectory.

The study area has an exploration potential of unconventional reservoirs, targeting tight carbonates from Upper Jurassic. To date, only one well has been drilled in the area of the interest and high quality 3D seismic data is available. The process consists of conducting seismic inversion, using the well and the 3D PSTM seismic data, and resulting in the generation of 3D subsurface impedance model. The well-log relationships between impedance and reservoir quality (effective porosity, source richness) and completion quality (brittleness) were determined and showed high correlation. Hence, 3D rock quality and geomechanical volumes were derived to characterize the behaviour of the reservoir target.

Seismic derived properties models yield a better description of the reservoir heterogeneity than using seismic reflectivity data only. The horizontal well trajectory was planned taking into account the observed and significant lateral variability revealed by the 3D models estimated based on seismic inverted data.

The results obtained using this methodology demonstrate the importance of integrating geophysical characterisation as a relevant supporting factor in the drilling decision making process. In particular, it validates the use of seismic derived reservoir and completion quality models as an additional tool in the definition of a horizontal well trajectory in a tight/unconventional deep gas target.
Forecast Of Ultra-Shallow Three-dimension Horizontal Well Extension Limit
Authors: Lulin Kong , Ye Tao , Xinyun Liu
Published: November 2017

Objectives/Scope: The length of horizontal section has a direct effect on heavy oil development efficiency. In order to calculate the extension limit of ultra-shallow horizontal wells in Venezuela heavy oil reservoir and provide theoretical reference for reasonable horizontal well design, this paper analyzed extension ability of ultra-shallow large displacement horizontal wells and give the reasonable extension length of horizontal section and reasonable drilling platform arrangement.

Methods, Procedures, Process: Analyze the main factors that impact the horizontal section length in heavy oil formation. Calculate the friction coefficient through measured data. By optimizing the well trajectory and BHA, establishing models for predicting torque and drag of horizontal wells and analyzing hydraulic parameter effect on extension ability of long horizontal section wells, the author calculate the mechanical extension limit and hydraulic extension limit of horizontal wells.

Results, Observations, Conclusions: Comparing the two extension limit, we find that ultimate extension length of horizontal section is mainly constrained by torque and drag. thereby the safety maximum extension length of horizontal section in heavy oil is predicted accurately. On this basis, we put forward a new interleaving well spacing design.

Novel/Additive Information: The result of this paper can provide theoretical reference for reasonable horizontal well trajectory design and horizontal length design. The novel interleaving well spacing design can help reduce the dead oil area significantly and increase the controllable reservoirs, which is of great importance to oil operator.
Optimal Matching of Bit and Reamer for Increased Reliability of Hole-Opening BHAs
Authors: Kueck A. , Ichaoui M. , Herbig C. , Hohl A. , Ostermeyer G. P. , Reckmann H.
Published: November 2017

Mechanical loads in hole-opening BHAs result in tool failures and generate maintenance costs and non-productive time. This paper presents a method to increase the reliability of hole-opening BHAs by optimally matching the bit and reamer. The weight and torque distribution between the bit and reamer is predicted using a stationary load model. New quality load curves facilitate the evaluation of bit-reamer combinations in a user-friendly way. The model and the load curves are validated on a unique set of field data, enabling determination of the model's accuracy.

The model is based on the mechanical specific energies at the bit and at the reamer. The model assumes the RPM and rate of penetration to be constant, the BHA is rigid in the axial and torsional directions and the lateral movement is blocked. Quality load curves are deduced that depict the load distribution in one plot. The model is validated on a unique data set that includes several high-precision measuring tools placed along the drill string. The unconfined compressive strength over depth that usually is not measured in other runs is available. The data set enables precise determination of the axial forces and torques directly at the bit and at the reamer. The observed mechanical specific energy, drilling efficiency, and aggressiveness of both cutting tools over depth are measured.

The model and the quality curves are used to predict the weight and torque distribution depending on the formation type at the bit and at the reamer. A comparison of the prediction to the measured data shows that the weight distribution is predicted with an error of 2% and the torque distribution is predicted with an error of 10.8%. The model accuracy is determined by introducing uncertain parameters into the model. The load predictions are again compared to the measured data. Using the coarse parameter set, the mean prediction error increases to 13%, which is very good, considering the simplifying assumptions of the model.

The validated model and the new quality curves enable an optimal choice of bit and reamers. The presented approach is fast and user-friendly and perfect for an application in advisory software in the well-planning phase. The increased reliability due to less mechanical overloads leads to reduced maintenance costs and less non-productive time of the reamer BHAs.
The Study of Nanosurfactant EOR in Carbonates by Advanced NMR Technique
Authors: Al Harbi Ahmad M. , Gao Jun , Kwak Hyung T. , Abdel-Fattah Amr I.
Published: November 2017

The application of conventional surfactant-based enhanced oil recovery (EOR) suffers from either the adsorption of the surfactant on the rock near the wellbore or from diffusion into small water-filled pores. An approach to mitigate the loss of surfactant and enhance deliverability to the oil phase is achieved by formulating the surfactant molecules into nano-sized particles, which are referred to as NanoSurfactant (NS) in this study. An essential step to unleash the potential of NS in EOR is the accurate understanding of its performance under conditions reasonably close to actual conditions.

In the current study, crude oil, synthetic brine, and petroleum sulfonate based NS were used. Eight limestone core plugs with a permeability range of about 125 millidarcies (mD) to 1282 mD were utilized in this study. Coreflooding was conducted under the near-reservoir condition. Advanced low-field nuclear magnetic resonance (NMR) techniques have been used to quantify the oil saturations by both secondary water injection and tertiary NS injection. The NMR techniques have also been used to assess the mechanisms underlying oil mobilization in carbonate core plugs. The protons in brine and NS solution were substituted with proton (H1) NMR invisible deuterium to enhance the contrast between oil and brine. The core samples were selected to investigate the effect of the NS soaking condition (soaking versus non-soaking), the NS injection rate, and the remaining oil saturation on the observed oil mobilization, respectively. All core plugs were initially saturated with oil and water, waterflooded, injected with NS (with and without soaking), followed by chase waterflooding. NMR measurements were conducted after each flooding stage.

The results of the current study demonstrate that the investigated NS has a great potential for EOR applications in carbonate reservoirs, and that soaking NS before chase waterflooding enhances its efficiency. Significant oil mobilization was observed when soaking was applied before chase waterflooding. The oil mobilization was much lower without soaking of NS for the cores with low quality and less oil wetting tendency. The analysis indicated that NS flooding can produce both of the trapped oil and oil adsorbed to the rock surfaces.
Extending Technology Limits – Application of Multistage Open Hole Horizontal Completion in Offshore Environment
Authors: Hall-Thompson Bryan , Ernesto Arias Urbina , Utaibi Abdullah A , Mashat Bahi , Vega Roberto
Published: November 2017

Multistage proppant and acid fracturing stimulation technology have contributed to increased hydrocarbon production in carbonate reservoirs. This technology has been deployed primarily in the Middle East’s onshore oil and gas fields for certain horizontal wells completed using Open Hole Multistage System (OHMS) with limited application in offshore environment.

OHMS was assessed for a low permeability carbonate reservoir offshore to evaluate well deliverability for a gas field and demonstrate its added value. Performing multistage stimulation in offshore environment is challenging and requires extensive planning and resources. This example looks at a 5-stage OHMS with single injection ports in +3,000 ft. segmented open-hole section to ensure efficient stimulation fluid placement. A High Rate Matrix Acid (HRMA) stimulation that creates highly permeable wormholes by pumping below fracture gradient is considered. These wormholes are conductive paths that improve near wellbore deliverability and avoid connectivity to any water in lower reservoir zones. The design considerations, field implementation of OHMS and HRMA are discussed. The technology is capable of increasing production performance by 2 folds of increase (FOI) relative to similar unstimulated cases.

This paper outlines the selection, execution, and challenges in deploying this technology. It discusses pretreatment formation evaluation, data requirement, data acquisition strategy, and key considerations for effective well completion and stimulation design. As an outcome, the paper highlights results and increased opportunities by applying this technology in offshore gas developments. It demonstrates value addition from rock property testing test, 1D Mechanical Earth Modelling (MEM), logging while drilling (LWD) well placement operations, and integration of wireline data, coring, imaging, sonic, and other data that ensure success.