bluuebunny/crossref_metadata_2025 huggingface dataset:
Phase Behavior Evaluation of Sodium Stearate Emulsion System: Stability Tests in chemical EOR
Authors: Mavaddat Marzieh , Baharamian Alireza , Riahi Siavash , Fakhroueian Zahra
Published: November 2015

This work presents a laboratory phase behavior study of Sodium Stearate/brine/oil system. The quantitative and qualitative observation of the phase behavior of the microemulsion in a three phase brine/oil/emulsion system is reported (Winsor III). The experiments were designed to investigate the stability, interfacial tension (IFT), and viscosity of the emulsion phase in a wide range of temperature (25-60 °C), water-to-oil ratio (0.2 to 5), salinity (10 to 200,000 ppm), and surfactant concentration. The range of parameters was selected as what typically occur during a chemical enhanced oil recovery (EOR) process. The effect of pH variations was also studied by changing that of the system from 1 to 11, using different acid and alkalines. As the pH increases, the stability of the emulsion phase increases as well as the emulsion phase thickness. The viscosity of the emulsion phase was also monitored qualitatively for different temperatures. Moreover, using longer chain alkanes confirms the capability of the surfactant for chemical EOR process.
Achieving Sustainable Zero Flaring through Spiking Gas Compressor at ADCO Field
Authors: Reddy Dr. Vijaya , Samad Khalid Abdul , Bamadhaf Mohamed Omar , Arunachalam Subbiah
Published: November 2015

Gas flaring is a major source of Green House Gas (GHG) emissions and impacts public health due to release of harmful pollutants. Gas flaring from oil and gas industry contributes to 1.5 % of the global GHG emissions.

As part of efforts to improve the environmental performance, ADCO commissioned spiking gas compressors to recover the flared gas and avoid emissions to atmosphere. The associated gas from one of the mid-eastern field is spiked into main oil line until such time as the new Gas plant is fully stabilised. The compressor train consists of reciprocating three-stage compressor, knock-out drum, air-cooler to cool down the compressed gas, metering skid, and glycol Dehydration Package.

Adopting spiking compressor in middle-eastern field provided substantial economic and environmental benefits to the UAE in general and ADNOC / ADCO in particular. In addition to recovery of 98% flared gas, the project resulted in reduction of CO2 and improved the local air quality in the area. The project was registered under the Clean Development Mechanism (CDM) of the United Nations Framework Convention on Climate Change (UNFCCC) in 2013 to claim carbon credits. Implementation of this project demonstrates the commitment of ADNOC Group towards climate change mitigation and sustainability.

The paper details the technical features of the project, the environmental, economic, and social benefits associated with recovery of associated flared gas, and the CDM registration process adopted to claim actual carbon credits.
A Novel Particle-Type Polymer and IOR/EOR Property Evaluation
Authors: Wu Xingcai , Xiong Chunming , Xu Hanbing , Zhang Jian , Lu Changdong , Lu Xiangguo , Li Jinkui , Cao Huiqing , Zhang Na , Cui Guoyou , Chen JingJing , Ye Yinzhu , Jia Xu , Lv Jing , Yang Zhongjian
Published: November 2015

Traditional polymer flooding technology is difficult to be used in high temperature and high salinity reservoirs, due to the property limitation of HPAM. It is the key of chemical flooding EOR to develop a new type of polymer, which can tolerate high temperature and high salinity and has high sweeping capacity.

Through microemulsion / suspension polymerization technique, a new particle-type polymer is developed. The polymer size is in the range of 30 nm to 112 μm, and can be divided into three size sections: nanometer, micrometer, and submillimeter. The microscope is used to observe the appearance, and the apparent viscosity of the dispersion is also measured, with which the temperature and salinity resistance and water absorbing and expanding property of the new polymer can be evaluated. A 2.1 m long core model is made to test the in-depth migration of the polymer particle. The resistance factor and residual resistance facter evaluation method for traditional polymer is borrowed to test the retention property of the new polymer in cores. Parallel dual-pipe artificial and natual cores are used to simulate the IOR/EOR property of the new polymer for sand and carbonate reservoirs.

The lab tests show the new polymer can tolerate high temperature, 120 °C, and high salinity, 200000 mg/L. The polymer particle can swell by 3-10 times in water by hydration, but do not change much in oil. The apparent viscosity of the new polymer liquid is 1-3cp, so it can be easily injected into deep reservoir. It can increase water flowing resistance, but not increase that of oil. When being used, the new polymer is a type of discontinuous liquid distributed with soft polymer particles, which is different from the traditional polymer, HPAM, which is a type of continuous viscous fluid. The IOR/EOR mechanism of the new polymer is different from that of the traditional polymer. As a type of dispersion displacing phase liquid, the new polymer can dynamically modify the permeable ability of different areas, by which the oil and water mobility can be modified effectively, achieving the aim of enhanced oil recovery.

The studies preliminarily established the property evaluation method for particle-type polymer, and discovered the IOR/EOR mechanism of the new particle-type polymer. The pilot test conducted in a reservoir with high temperature, 120 °C, and high salinity, 14.9-21.7×104 mg/L, with Ca2+ / Mg2+ concentration of 2500 mg/L, obtained obvious oil rate increase and water cut decrease effect, and achieved technical and economical success.
Novel Workflow for the Development of a Flow Control Strategy with Consideration of Reservoir Uncertainties
Authors: Gohari Kousha , Jutila Heikki , Mascagnini Carlos , Gryaznov Andrey , Goodwin Nigel , Howell Murray , Kidd Peter J. , Bijani Behrooz
Published: November 2015

Flow control along the wellbore is an important factor for a successful field development. Creating a flow control strategy can be especially difficult when a high level of reservoir uncertainty exists.

A novel workflow was developed to help determine the flow control / intelligent completion strategy best suited for field development, by taking into account the reservoir uncertainties and control parameters for optimization. The workflow simplifies and reduces cycle time, yet ensures that the inflow control strategy for the field is fit-for-purpose. This novel methodology enables a rapid understanding of the uncertainties and reduces the cycle time of evaluation and high-level screening, and ensures a more responsive decision process to improve production and reduce costs.

The described workflow is an optimum approach that is easily applied in an efficient semi-automated manner for any field. This method utilizes steady-state analytical and dynamic reservoir modelling for the determination of geological/subsurface uncertainties and selection of an optimal flow control strategy. Initially a base case model is constructed with the most likely/expected reservoir properties and control parameters. A series of experimental design cases are run, and then an objective function is created, followed by a large number of optimization runs to investigate the potential solution space. The analysis of these cases quantifies the effects of each uncertainty parameter. Using the analysis performed on uncertainty, a number of the scenarios are investigated in detail to study various flow control completions (passive and active) and determine the system that is best suited to achieve the optimum recovery efficiency. A full optimization under uncertainty is conducted so that the flow control settings are optimized against the full probabilistic subsurface uncertainties.
Enriched Inflow Performance Relationship (EIPR) Curves for Simultaneous Selection of Target Rate & Pump Setting Depth While Visualizing Free Gas Conditions
Authors: Caicedo Sergio
Published: November 2015

During the pump sizing, artificial lift (AL) engineers usually deal with the problem of deciding the setting depth of the pump and the target production rate. There is a trade-off regarding the pump's depth; the deeper the pump, the lower the free gas, the higher the potential rate, the higher the submergence but the higher the cost, and the higher the temperature. The present paper shows a method to suggest setting depth and target rate simultaneously.

Sometimes there are so many constraints that the setting depth is imposed by the reservoir, well completion, integrity or safety conditions. In other circumstances, there can be a wide range of possibilities, which will be discussed in this paper. One of the most important parameters to evaluate is the free gas into the pump because it will greatly affect the performance of the pump, besides requiring more volume capacity, the free has other consequences such as locking the ESP, affects the PCP elastomer, reduces the compression ratio in SRP and increases the required power fluid pressure and/or rate in JP. The free gas limits and solutions vary for each method, but all of them require knowing the actual value, independently of the pumping method (i.e. ESP, PCP, SRP or JP). The engineer has to start by imposing the pump's depth and after some computations check if that depth is feasible or not for the target rate. If it is not feasible two actions can be done: to reduce the target rate and/or to install the pump deeper. On the other hand, if the pump can handle the free gas then a question arises: could the pump be installed shallower keeping the same target rate? This question can only be answered by computing free gas and displaying it in some way together with the reservoir inflow.

In order to avoid this trial and error process, this paper defines and suggests the Enriched Inflow Performance Relationship (EIPR) curves at pump intake for different setting depths, each one showing points highlighted using a colour scale to indicate free gas conditions into the pump. The free gas displayed mainly depends on the Pump Intake Pressure, Bubble Point Pressure, GOR, Water Cut, downhole gas separation efficiency. Since the reservoir performance is included, these EIPR Curves easily allow simultaneous selection of target rate and pump setting depth while visualizing free gas conditions which avoids the trial and error process showing a more realistic application window of the method.

All previous papers just display standard inflow curves. There is no previous work showing additional attributes in the IPR curve that helps the engineer to visualise the corresponding conditions of the pump.
Maintaining Aging Export Systems - Replace, Maintain or Renew?
Authors: Collins Jonathan , Morvan Remi , Whelan Tim
Published: November 2015

Offshore Loading Systems represent a critical asset of tank farms and refineries operations, with potentially significant financial consequences in case of unavailability.

The paper looks at the main issues associated with Integrity Management of aging export and loading systems (both topside equipment such as CALM buoys and subsea equipment such as pipelines and PLEMs) and discusses the main drivers forcing Operators to consider either replacing or upgrading their existing systems.

Following a steep decline in oil prices at the end of 2014, which are likely to remain at present values for the near future, many Operators are looking at options to postpone planned procurement projects to replace aging equipment and are pursuing alternative strategies to maintain the output and uptime of their aging facilities. This paper discusses Integrity Management best practices, available to Operators to survey and maintain as well as manage the service life extension of their systems.

The paper also addresses the options available when remediation works must be carried out. In particular, attention is focused on novel refurbishment activities which can be performed onsite whilst minimising the level of system downtime. Examples include: Refurbishment of CALM Buoys in dry-dock or on-site, relining of corroded subsea pipelines and removal/replacement subsea of damaged or corroded sections of pipeline.

In conclusion, a number of cost comparison studies are presented to demonstrate the potential financial benefits of extending the remaining life of a system rather than replacing aging equipment with new.
An Example for Successful Integration of Borehole Seismic Technology in Exploration and Development
Authors: Lange Christian , Katsuko Suzuki
Published: November 2015

Borehole seismic surveys provide vital depth and velocity parameters needed to link surface seismic data with downhole log and well data. Furthermore they can deliver high-resolution subsurface images, detect anisotropy caused by natural fractures and help to monitor fluid movement depending on the chosen survey geometry.

A borehole seismic survey, whether simple checkshots or a more complex VSP, is usually part of the initial data acquisition program in exploration and appraisal wells, but it is not uncommon that only the depth-time data from such a survey is used in seismic interpretation. This paper is intended for geoscientists working on subsurface projects to highlight information that can be gleaned from a VSP wavefield in addition to only a depth-time correlation.
Delivering a Compliant Composite Solution in a Noncompliant Situation
Authors: Johnson Peter , Oharriz Osmay
Published: November 2015

This paper discusses about two-part composite systems consisting of thermoset epoxy resins reinforced by carbon and glass fiber for applications onto pipeline, pipework, piping systems, and vessels in pressurized service. The document presents details related to qualification and testing of such systems in compliance with internationally accepted standards. It also covers key components of a composite repair from the application standpoint and describes what is required to deliver a compliant solution from inception to final inspection.

Composite repairs are rapidly becoming an acceptable maintenance option even for safety critical equipment because they repairs offer an engineered, durable, and affordable solution. Additionally and more importantly they comply with international engineering standards. Designed for application onto pipelines, pipework, and pressurised vessels, composite repair systems are typically composed of resin and reinforcement sheet.

Pipeline is the pipe or components, including bends, flanges, valves, and reducers among others, used to transport fluids between plants. Hence, pipelines are generally long and of larger diameters. Piping is the pipe or plurality of pipes, joints, valves, gaskets, fittings, etc., used for transporting fluids within a plant, and they can be above or below ground. Other pieces of equipment where two-part component composite repairs can be used include pressurized vessels and tanks, and/or some of their components such as saddles, main body connections, supports, nozzles, and tees among others.
Integrated Leak Detection in Gas Pipelines Using OLGA Simulator and Artificial Neural Networks
Authors: Afebu K. O. , Abbas A. J. , Nasr G. G. , Kadir A.
Published: November 2015

Gas pipeline leakages do not only represent loss of valuable non-renewable resources but also a potential source of environmental pollution and fire disaster, thus making it very important to have a quick and accurate leak awareness scheme in pipeline systems. In a novel approach of providing industry with more reliable, friendly and cost effective technique in handling pipeline leakage especially in countries were pipeline vandalism has been widely reported. This require urgent detection and intervention, the potential of an Artificial Neural Network (ANN) in detecting and locating leaks from everyday flow line measurements was explored in this research paper. Pipeline responses under zero (no) leak condition, and realistic different leak conditions were simulated on a gas pipeline using OLGA simulator. Simulated leaks were seen to be characterized with unique flow rate, velocity, pressure and temperature signatures that were identifiable by the neural network. The network during training was able to learn the correlation between these signatures and the leak parameters and then use the learning in predicting and locating leaks from new signature data. The network predictions showed final RMSE values of 6.14 and 0.977 for the single and multiple leaks model respectively. The correlations between the actual and predicted leak sizes gave R values of 0.95 and 0.60 for the single and multiple leaks respectively while those of the actual and predicted leak locations were 0.97 and 0.96. The system was able to locate 90% of the induced leaks to a distance that is less than 10 m away from the actual leak locations while 62% of the ANN predicted leak sizes differed from the actual value by less than 50% of the actual leak size and the remaining 38% differed by about 65 – 400% the actual sizes. This thus implies that the set has a better precision in predicting leak locations than predicting leak sizes. Based on obtained results, it can be said that with sufficiently large number of measurements, neural networks are of great potential in predicting and locating leaks. Results also showed that leak detectability tends to improve with increasing leak size and increasing distance from the source and the relatively low correlation obtained for the multiple leaks model can be attributed to the partial masking of smaller downstream leaks by larger upstream leaks.These characteristics of leaks are predominant to the countries with cases of vandalism, and could be a potential approach in handling pipe leaks.
The asphaltene risk map recommendation: Asphaltene Risk Estimation on an Offshore Field Utilizing Experimental Results
Authors: Takabayashi Katsumo , Tani Kengo , Arii Hiroaki , Baslaib Mohamed
Published: November 2015

It is widely known that pressure drop and compositional change of reservoir fluid causes asphaltene precipitation. Regarding compositional change, gas injection is believed to be a typical trigger of asphaltene deposition. The injected gases are mixed with reservoir fluid and gradually change the composition in the reservoir as gas front is heading. For such fluids, compositional changes are believed to take place not only near gas injectors but also in a wider area. Thus, asphaltene precipitation risks should be considered on field scale.

This paper demonstrates how to generate "Asphaltene Risk Map on field scale" based on the correlation between Asphaltene Onset Pressure (AOP) and fluid composition. A Middle Eastern offshore oil field which encounters asphaltene problems was selected as an example because the above two key parameters are mainly working in the field for destabilizing asphaltene. For creating risk map, compositions of reservoir fluid near the asphaltene problem wells were calculated from reservoir simulation. The calculated compositions were applied for the asphaltene model with calibrating measured AOP. Various combinations were evaluated on the plots of AOP versus composition to find well-converged correlation.

Eventually, the C1-C19 component was selected to achieve the most reasonable correlation to AOP for this case. According to pressure variation from the correlated AOP, risk ratings were proportionally distributed on the plot. Based on these risk ratings, "Asphaltene Risk Map" was translated from the relationship between C1-C19 component and pressure. The created risk map shows a reasonable tendency to replicate the timing of actual asphaltene precipitation. In addition, two types of asphaltene precipitation mechanism were confirmed on the Risk Map. Namely, higher risk was estimated in two producers; one is located in the gas breakthrough area due to gas cap expansion, and the other is isolated from the gas breakthrough area but is in the vicinity of free gas observed area where compositional change occurs.

This Asphaltene Risk Map is considered useful to optimize gas injection plan, in particular. Time-lapse prediction of asphaltene risk can suggest timing and/or priority to prepare mitigation plan.
Innovative Energy Optimization Program Results in Huge Cost Savings and Sustainability Benefits
Authors: Pushkarna Arun , Elbadiich A. , Motairy M. A. , Abdullah S. , Ali M. , Hendawy M.
Published: November 2015

National Drilling Company has put in place an Energy Management System. The main objective is to ensure an optimum use of energy by trimming waste, better use of natural resources and avoidance of unnecessary operating costs. Additionally the initiative targeted improving environmental performance.

Methods, Procedures, Process:

NDC examined the prevalent practices and energy sources within the company. It then prepared a chart showing the relationship between each energy source thus identifying the largest consumer. This led to the identification of the best improvement opportunity that the company could put in place. Not surprisingly this was the rig engines. Once this was done, the company devised a simple process to monitor and report on the actual energy consumption per site. This was compared with the actual operation at the time of reporting and the correlation between these two parameters identified an opportunity to optimize the deployment of engines. Moreover, with numerous rigs engaged in similar operations a process was put in place to compare between similar rigs and operations. The anomalous use of engines was highlighted and site staff advised against inappropriate use.

Results, Observations, Conclusions:

Although the process was started as an initiative to cut down on diesel consumption (diesel being identified as an energy source in ISO 50001) and conserve energy consumption across the company, the results when compared after one year of operations yielded additional benefits. The overall savings of the company were as follows:

Fuel Savings - Almost 5 million gallons of diesel were saved in the full year.

Cost savings - Over 55 million Dhirams savings were realized

Energy Savings - Almost 700,000 Giga Joules of energy savings were recorded

CO2 Reduction - 50,000 tonnes of reduction in CO2 emissions was recorded for 2014 vis-à-vis 2013.

Other benefits of the project was in reduction of maintenance costs, reduction of lubricating oils for engines, Better utilization of capital assets and a longer life of the engines across the company.
First Principle Models for Emission and Performance Monitoring
Authors: Nielsen Jan Sandvig , Weel Mogens
Published: November 2015

Combustion processes such as gas turbines, furnaces, flares and boilers in the oil and gas industries are significant sources of pollutants that can impair human health and the environment, including sulfur dioxide (SO2), nitrogen oxide (NOx) and carbon monoxide (CO). Further, these sources will have an impact on global climate via its emission of greenhouses gases – primarily carbon dioxide (CO2).

SO2 and NOx, when emitted to the air, react with water and other compounds to produces various forms of acidic compounds and particles, which can remain in the air for days or weeks. Depending on wind direction and speed, these harmfull substances can be spread in wide areas and are not necessarily limited to the country of the emission sources. When the pollutants fall on to earth or water they will have impact on air quality, visibility, acidification, sensitive forest and coastal ecosystems.

SO2 and NOx emissions form fine particles in the atmosphere. Particulate matter is the term used for a mixture of solid particles and liquid droplets found in the air; fine particles (PM2.5) are smaller than 2.5 microns (millionths of a meter) in diameter. The gas fired combustion sources emit particles directly into the air, but their major contribution to particulate matter air pollution is emissions of SO2 and NOx, which are converted into sulfate and nitrate particles in the atmosphere. These particles make up a large part of the fine particle pollution in most parts of the country. It is scientifically well recognized that there is a correlation between elevated fine particulate matter and increased incidence of illness and premature mortality. In addition, NOx and organic volatile compounds forms ozone with the presence of sunlight. This ozone will be present at ground level and is a major part of the smog and is also linked to potential health hazards including respiratory illness.
Borehole Controlled Source Electromagnetic (CSEM) Surveying for Monitoring HC-Saturation in the Bockstedt Oilfield (NW Germany)
Authors: Tietze K. , Ritter O. , Patzer C. , Veeken P. , Verboom B.
Published: November 2015

Main objective is to support reservoir monitoring in an EOR production scheme. Enhanced oil recovery calls for efficient monitoring of hydrocarbon saturation changes. In the onshore Bockstedt oil field there exists a substantial difference in resistivity at reservoir level: for initial oil saturation it exceeds 100 Ohmm reducing to 0.6 Ohmm once fully displaced by formation brine. Applicability of the controlled-source electromagnetic method to monitor such resistivity changes is investigated. Targets are Lower Cretaceous shallow marine clastics at approximately 1200 m depth.

Finite difference forward modelling shows CSEM is sensitive to expected resistivity changes, but the effect is difficult to resolve with surface measurements only. Resolution increases significantly if sensors or transmitters are placed in observation wells closer to the reservoir. Behaviour of the vertical electric component (Ez) in shallow boreholes and/or use of complex source configrations look rather promising.

In 2014, a borehole-to-surface CSEM configuration was deployed successfully across the Bockstedt oil field, whereby the current was injected via the metal casing of an abandoned production well. The set-up also allowed conventional magnetotelluric (MT) data acquisition when the transmitter is turned off at night. CSEM response functions are of good quality with high repeatability. Recordings from conventional and new borehole transmitters indicate different current distributions in the subsurface. Results of the tested source configuration are in agreement with predictions by numerical simulations. Preliminary 3D inversion is consistent with previous numeric simulations.

A timelapse CSEM survey is scheduled for 2015, inclusive drilling of a shallow observation well for Ez component monitoring with a new borehole sensor. In parallel, a timelapse workflow for 3D CSEM inversion is developed.
A Multi-disciplinary Integrated Approach To Understand The Potential Of The Najmah-Sargelu Reservoirs Of The Dharif and Abduliyah Fields (West Kuwait)
Authors: Matar Saad , Ray Dipak Singha , Abdulmalik Ameena , Mukherjee Pritish , Perfetti Erwan , Maux Thierry Le
Published: November 2015

The Najmah and Sargelu, two tight carbonate reservoirs of Jurassic age, are oil bearing in the West Kuwait fields Dharif and Abduliyah. Due to their complexity, presence of numerous natural fractures and low matrix porosity and permeability, these reservoirs have been underdeveloped in both fields. A multi-disciplinary integrated study has been performed to thoroughly investigate their potential and design the appropriate future development plans.

This paper shows how the use of the 3D seismic data and the rock typing exercise has been maximized to constrain the derived models and reduce the uncertainties. The main reservoir horizons (top Najmah, top Sargelu and top Dharuma) have first been interpreted using the 3D seismic cube and major faults were picked on vertical seismic section and time slices. A seismic characterization work aimed at enhancing seismic data and better describing both matrix and fractures in between wells was also performed. The seismic fracture characterization study led to a set of seismic fracture index maps detailing the fault/fracture corridor network. The matrix characterization study provided an average shale proportion map in Najmah to guide the shaly facies proportions in the geological model.

From the available well data, mainly core description and classical logs, a detailed sequence stratigraphy and petrophysical interpretations were performed. Electrofacies were then computed at wells before being propagated in 3D in a detailed geological model combining both fields.

Finally analysis of the natural fracture network was made using multiple sources of data: core description for fractures, image logs interpretation, seismic maps, transient well tests, production data … A Discreet Fracture Network (DFN) model was derived and then dynamically calibrated. The equivalent fracture properties (porosity, permeability and fracture spacing) were computed and imported into a dual porosity – single permeability simulation model.

Using the limited production and pressure data in both Dharif and Abduliayh fields, the dynamic models were adjusted to fit the production history: uncertain oil-water contacts depth were modified and small modifications of fractures properties in around one of the well was performed. The calibrated dynamic models were then used to test several development scenarios. Dharif potential, due to the presence of a thin oil column, was shown to be limited. Abduliyah potential, on the other hand, is likely to be greater if the fracture network is proved to be as permeable as in Dharif. If this is confirmed, a development with horizontal producers located at the crest of the structure is likely to be the most suited method.
Innovative Solutions to Overcome Production Constraints
Authors: El Thany Ezzat , Al-Dhaheri Abdulla Mubarak
Published: November 2015

ADGAS operates three LNG trains of which Train-3 is designed to produce twice the capacity of any one of the other two trains. ADGAS LNG Trains 1&2 process LP Gases and HP Gas from ADMAOPCO, to produce 180 T/Hr of LNG in each train. ADGAS LNG Train-3 processes only HP Gas to produce 384 T/Hr of LNG. Apart from LNG, Propane, Butane, Paraffinic Naphtha and Sulphur are also produced as secondary products. Though the installed capacity of Train-3 was 320 tph, with an initial study and modification the production was increased to 380 tph LNG since its commissioning.
The Impact of Effective Fracture Length versus Effective Fracture Height on Ultimate Recovery in Tight-Gas and Unconventional Reservoirs
Authors: Shaoul J. R. , Park J. , van der Hoorn K.
Published: November 2015

This paper evaluates the effect of different proppant pack cleanup scenarios on welltest analysis results and long-term recovery in tight gas and unconventional reservoirs. Simulated buildups are created in a detailed reservoir simulation model. The simulated buildups are analyzed in a commercial welltest analysis package to obtain an apparent effective propped fracture length, as is common practice in the industry. Two different proppant pack cleanup scenarios are compared, both of which result in a short apparent effective fracture length based on welltest analysis. The effect on long-term recovery for the different cleanup scenarios is then simulated using detailed 3D reservoir simulations, showing that there is a significant difference in recovery, in spite of the comparable welltest analysis results.

In a previous publication (Shaoul et al. 2015), we showed the effect of stress sensitive reservoir permeability on reducing the fracture length estimated from welltest analysis. Now, using detailed 3D reservoir simulations, we simulate welltests with different proppant pack cleanup scenarios, from piston-like flow to complex channeling and analyze them in a welltest package. Welltest analysis estimates effective fracture area, and then calculates length based on an assumed fracture height. When only a portion of the fracture area cleans up, this gives a reduced fracture length. The maximum fracture extent (the furthest distance from the well that the proppant pack has cleaned up, relevant for drainage extent) may be close to the full propped length, while the small effective area calculated from the welltest can actually be caused by a reduced effective fracture height. The impact of this assumption on the buildup analysis and ultimate recovery is examined by simulating two different proppant pack cleanup scenarios.

This work supports field observations that have been made by Barree showing a correlation between ultimate drainage area and fracture size. This work suggests that trying to achieve maximum possible propped length is still important in tight and unconventional reservoirs to maximize long-term recovery and connected gas in place, even when well testing shows a short effective fracture length. Including the effect of effective fracture height, or using more realistic assumptions about proppant pack cleanup, would help to avoid underestimating the actual effective fracture length. Welltests showing short fracture lengths have led some people to reduce treatment volume and increase proppant concentration to achieve higher fracture conductivities. They hope to increase the effective length even while reducing the created propped length. Using more realistic proppant pack cleanup scenarios, we show that this approach may actually be counterproductive in tight gas and unconventional reservoirs, because it reduces ultimate recovery due to a reduced fracture extent.
Recent Technologies for Land Seismic Imaging Over a Complex Near Surface Overburden
Authors: Bouzidi Y. , Vesnaver A.
Published: November 2015

Removing signal distortions due to near surface complexities is the key challenge for land seismic data imaging. In the Middle East, where several major oil fields are located onshore, these complexities require developing new technologies: as extreme shallow velocity variations occur occasionally elsewhere, not enough research and development has been carried out to fully compensate them so far. In addition, the common recording geometry for deep targets produces a near-surface information gap (Vesnaver 2005). In this paper we review recent advances and some ongoing research that address this problem, with applications to real cases in the Arabian Peninsula.

The first technique reviewed is the inversion of the vibrator plate controller data, normally available in the Vibroseis seismic records, but rarely used for improving the Earth imaging. We show that it helps removing high-frequency spatial distortions due to local soil anomalies. As recording this data is part of standard field operations, its use comes almost for free, as the related processing is not heavy in terms of computing power.

A second cost-effective approach is the integration of seismic and satellite imagery. The resolution commercially available for Earth images in various electromagnetic bands is fitting the normal bin size adopted in 3D seismic surveys, e.g., 25×25 m. Thus, correlating the soil properties in terms of back-scattered radiation with physical properties as P-wave velocities or Q factor, allows improving the resolution of the shallowest layer in our Earth model. As this layer – (the so-called weathering) – is normally the most heterogeneous, improving its estimate allows removing better the related distortion for imaging the possible underlying oil and gas reservoirs.
Sensitivity Analysis of Unstructured Meshing Parameters on Production Forecast of Hydraulically Fractured Horizontal Wells
Authors: Sun Jianlei , Schechter David , Huang Chung-Kan
Published: November 2015

In the context of multi-stage hydraulically fractured horizontal wells, unstructured grids such as PEBI (perpendicular bisector) grids or Voronoi grids have been widely applied to generate simulation meshes for fracture networks. In previous work we developed a robust optimization-based 2D meshing algorithms to handle non-orthogonal, low-angle intersections of extensively-clustered fractures with non-uniform aperture distributions. However, vertically extruded 2.5D PEBI grids become necessary with more wells being drilled into dipping layers. Besides, it is necessary to provide practical application suggestions for choosing an unstructured mesh to accurately resolve flow regimes of production.

In this work we extended 2D PEBI workflow to 2.5D, and then validated it against two models: (a) a synthetic model with one horizontal well and 120 orthogonal intersected hydraulic fractures built by Tar-tan grid and (b) a field-scale model with three horizontal wells and 120 non-orthogonal intersected hydraulic fractures in a slightly dipping reservoir created by a commercial software plug-in. For the synthetic model, we simulated production performance at a constant bottom-hole flowing pressure up to 20 years. For the field-scale model, we first performed history matching and then predicted production at a constant rate up to 20 years. We compared pressure diffusion front, bottom-hole flowing pressure as well as CPU performance.

Reasonably good matches between PEBI grids and other grids are observed in both pressure diffusion front and production behavior. Sensitivity analysis suggests that refinement around the fractures has modest impact to early time production while background density has dominant impact to the late time production. Background grid type and grid orientation have less influence as long as they have the same grid density. Less number of 2.5D PEBI cells can be achieved by removing unnecessary refinement around fractures, increasing reservoir background size and reservoir background size ratio, replacing unstructured background grids with structured grids, and reducing the complexity of the fracture networks without loss of the accuracy and therefore result in much favorable CPU performance. The existence of opened natural fractures was evaluated to simulate the out-of-zone production. The results suggest that effective drainage area can be significantly greater with the synergy of the natural fractures.

This study is the first to apply unstructured grids to simulate multiple horizontal wells with irregular hydraulic fractures. Besides, this paper provides detailed discussions of implementation algorithms as well as comparisons between 2.5D PEBI and LGR based grids in the context of fracture modeling. And most importantly, this study answers the question regarding how to choose an appropriate 2.5D PEBI mesh to yield both accurate results and good CPU performance.
Optimization of Acid Fracturing with Unified Fracture Design
Authors: Ravikumar Arjun , Marongiu-Porcu Matteo , Morales Adrian
Published: November 2015

Acid fracturing is the most recognized and successful reservoir stimulation technique for conventional carbonate formations. Resulting fracture conductivity is the key parameter that controls final well productivity, while the competing diffusion and reaction phenomena control the "vital" acid coverage along the full areal extension of the fracture. However, not all reservoirs lend themselves to the same fracture geometry and conductivity, and this is where the "Unified Fracture Design" (UFD) approach is irreplaceable.

Classic fracture design optimization with the UFD approach involves the maximization of well productivity. For any mass of proppant to be injected as part of the treatment, the algorithm determines the unique fracture length and width (with height as a parasitic variable) that will provide the maximum productivity index.

In this paper we recast the UFD approach for specific acid fracturing applications, where the maximum productivity index is now determined as a function of the optimum fracture geometry determined for any volume of injected acid. The optimum fracture width profile is then obtained by solving the convection-diffusion equation for acid propagation, and subsequently used to study the required acid coverage through the fracture as a function of such optimum fracture width profile.

Acid reaction retardation plays a crucial role in ensuring proper acid coverage throughout the optimum fracture length, and this paper focuses on the two major reaction retardation fluid systems: Acid-Internal Emulsions (AIE) and gelled acids.

The workflow presented in this paper provides the basis for designing optimum acid fracturing treatments as a function of the volume of acid injected, the acid injection rate and the selected acid retardation method.
Forecasting the Reliability of a Wastewater Disposal System and Predicting Future Corrective Actions using Hydraulic Simulation
Authors: Al-Hajri Nasser M. , AlAjmi Mohammed D. , Al-Subaie Fehead M. , Al-Zaharani Rashad M. , Al-BenSaad Zakareya R.
Published: November 2015

Continuous monitoring of wastewater disposal (WWD) systems capacities is necessary given the increase in water production from mature fields. The grave and critical importance of such systems necessitates proactive diagnosing and forecasting of WWD system performances. The precise outcomes of hydraulic simulation have proven reliable in forecasting operational scenarios related to WWD systems. The accurate predictions of hydraulic simulation, coupled with identified time frames and monetary investments, pave the way for accountable and successful managerial decisions.

Plant-A injects wastewater into five disposal wells at a given capacity. Historical system performance showed an increase in the pump discharge pressure that has reached near its maximum operating limit. Future production demands entail the need to avail extra injection capacity to this WWD system.

A full system analysis of Plant-A disposal network, utilizing hydraulic simulation techniques, was performed to model the current injection performance. The inflow and outflow performance relationships for five disposal wells were generated and calibrated using actual injection data. Network flow analysis was performed to account for both frictional and gravitational pressure losses in pipelines and flow restrictions using sophisticated software. This comprehensive study of the disposal system was aimed at exploring all possible root causes of the discharge pressure increase. In addition, the hydraulic simulator forecasted several feasible and recommended scenarios to eliminate this high discharge pressure. The contemplated scenarios were tapping into a nearby disposal system (either from the pumps suction or through transfer lines to the close by disposal system) and installing horizontal pump systems at the injection wellheads.

This paper will present in depth the hydraulic simulation results of the above-mentioned scenarios and highlight their feasibility as viable short-term options. In addition, a detailed account of the associated time periods and respective costs of conceived short-term plans is shown. This high accuracy model improved the decision-making process, and an optimized solution was put into effect based on the simulation results.
Optimization of Surfactant Flooding for Carbonate Reservoirs
Authors: Dong Han , Al Yafei Arafat
Published: November 2015

Surfactant injection can be used as an EOR technique by either altering the wettability of reservoir and/or reducing IFT of water and oil. How to balance the functionality of wettability alteration and IFT reduction of a surfactant flooding process for oil wet carbonate reservoirs is still paradox for surfactant technology selection. In this study, the effects of IFT reduction and wettability alteration by surfactant on EOR for a carbonate reservoir were studied by using two kind surfactant systems individually. For IFT reduction surfactant, the surfactants which can reach IFT at different level and ultralow IFT were synthesized based on molecular design method by only changing the structure of surfactant and without any formulation process. Moreover, these surfactants are also has a little effect on wettability alteration proven by contact angle test. The surfactants for wettability alteration study are selected based on contact angle method and also on the principle of "less effect on IFT property". The static and dynamic imbibition tests are carried out to understand the contribution of wettability alteration and IFT reduction mechanism individually to enhance oil recovery, hence, the surfactant flooding technique for an oil wet carbonate reservoir could be optimized.
Optimisation of Shutdown Inspection Activities in the LNG Industry
Authors: Sabry Houssam
Published: November 2015

ADGAS is the pioneer LNG producer in the Middle East. ADGAS owns and operates 3 LNG Trains. Trains 1 and 2 were commissioned in 1977 (38 years ago). Train 3 LNG was commissioned in 1994. Furthermore ADGAS commissioned its first sales gas processing and compression facility (the OAG) in 2010. This was followed by the mega IGD gas processing and compression facility. The ADGAS overall production now accounts for MMSCFD 2100 of processed gas. ADGAS over the years has developed a long term experience in LNG and gas operations, maintenance and integrity management protocols. ADGAS followed a strict Planned Shutdown/Turn Around (TA) at regular intervals for its LNG trains. This paper shares and highlights ADGAS initiatives for optimizing the integrity and inspection related works in its TAs.

TA's are an opportunity to carry out offline maintenance schemes, perform internal inspection for equipment. On the other hand TA's represents a production/ opportunity loss, hence, optimization of TA scope and duration is very important. ADGAS Integrity group has launched a TA optimization exercise. These initiatives included the introduction of Digital Remote Video Inspection, where no physical entry is required to inspect pressure vessels, thus saving time and preparations for physical entry. Another initiative included the introduction of a safe radiography technique. Generally, radiography is done to inspect welded joints. Conventional radiography requires suspension of all TA works and full evacuation from the area. Safe radiography can be done while all activities are ongoing. This introduced a major cost reduction in terms of reducing the TA duration. In Safe radiography the barricaded zone is only 1.5m in radius. Another initiative is by introducing flares online tip inspection using unmanned aerial vehicles. Full and effective RBI implementation has significantly optimized the TA scope of work. This paper and presentation will share ADGAS' LNG experience in TA inspection works optimization.

Lessons learnt, cost reduction and TA scope optimization will all be shared with the audience. The paper would share the lessons learnt from the TA inspection and integrity scope optimization innovative initiatives.