bluuebunny/crossref_metadata_2025 huggingface dataset:
Log Technology Advances and Novel Data Analysis in Integrated Approach Unlock Full Potential of a Peculiar LRLC Reservoir Offshore Nigeria
Authors: Otevwemerhuere J. , Nwosu C. , Olare J. , Jefford Leigh , Parkins Steve , Cavalleri C. , Shrivastava C. , Espinosa H. , Mougang M.
Published: November 2015

Low resistivity low contrast (LRLC) reservoirs have been successfully produced for many years; however detection and detailed description of their properties and potential would remain a challenge in absence of an exhaustive formation evaluation program. Proper understanding of the geological evolution of such reservoirs to explain their distribution and variations in petrophysical properties is also vital.

Low resistivity pay reservoirs encountered in West Africa are often characterized by variation in resistivity values in vertical and horizontal directions due to fine grains and conductive layers within the coarse grained sands and clearly marked sand-shale laminations. This is accurately solved by tri-axial induction resistivity measurement in combination with high resolution measurements able to define any contributing layer level-by-level through robust anisotropic interpretation methods. However, heterogeneity, mixed clays effect, and complexity in rock texture require new technology and innovative interpretation models in multi-domain approach.

Advances in logging technologies, interpretation software, and analytical methodologies enable better and more refined reservoir models to be fashioned and tweaked as needed on a case-by-case basis. The case study analyzes log responses, implication of heterogeneity and mixed clays content on the generation of LRLC pay reservoirs in deltaic environment offshore Nigeria.

Precise application of advanced log measurements and integration of core data in a common workflow, built around the concepts of evolution of LRLC reservoirs lead to accurate pay quantification. Borehole image interpretation suggests that the low resistivity contrast is attributed to dispersed clays coating around the sand grains in the toe part of a delta front in major coarsening up and feeble fining up sequences. This is also confirmed by variations of elastic properties of the matrix.

Petrophysical logs recorded at high resolution correlate inferring the main causes of LRLC pay are clay content and distribution, and small grain sizes intermingled to the reservoir rock, hence resulting in low resistivity values in all directions and drastically increased irreducible water. The logs based model is confirmed by calibration to core analysis results. The confident results of the study confirm the power of collaboration between petrophysics, rock mechanics and geology in innovative interpretation workflows for enhanced reserves estimate and Producibility prediction in heterogeneous media.
38 Years of Experience with Seawater Cooling Cu/Ni Tube Bundles in LNG
Authors: Sabry Houssam
Published: November 2015

Many LNG and gas production facilities depend on sweater cooling as a cooling media in its processes. Seawater cooled heat exchangers represent the back bone to achieve the required operations performance. Copper based alloys are the classical material of construction for sweater cooling heat exchangers. Al-Brass, Cu/Ni 70/30 and 90/10 are all copper alloys famous for being used in seawater cooling heat exchanger tube bundles. However, copper based alloys are prone to numerous degradation mechanisms. This paper shares ADGAS’ long term experience with copper nickel heat exchangers in sweater.

The study includes the operations and inspection history of over 100 copper based alloy heat exchangers. It provides the gas and LNG industry with a wealth of information in terms of the observed damage mechanisms, failure history, performance in addition to the operating parameters affecting the integrity of copper based heat exchangers.

The paper would conclude the best performance parameters of these heat exchangers and would provide useful information to establish the optimum integrity operating window for the copper based heat exchangers. The paper would include the performance of all used copper based alloys in terms of Al-Brass, Cu/Ni 70/30 and Cu/Ni 90/10. It will also compare the economics of using copper based alloys versus the use of other materials of construction in the same application like titanium and 6 Moly super austenitic stainless steel alloys.

Little information is available on the long term performance of copper based heat exchangers in the Gulf region waters. Furthermore, it will be an opportunity based on this long service life of 38 years to confirm the published academic literature on the performance of these heat exchangers. The paper shall hence represent a very useful tool for the materials selection in Gulf water cooled heat exchangers.
State of the Art Special Core Analysis Program Design and Results for a Middle Eastern Carbonate Reservoir
Authors: Gao Bo , Kralik Jim , Vo Loan , Shebl Hesham , Al Shehhi Rashed , Al Jawhari Mohammad Omar , Fullmer Shawn
Published: November 2015

A state-of-the-art special core analysis (SCAL) program for a Middle Eastern carbonate reservoir was designed to provide critical and high quality SCAL data for use in field-wide reservoir studies. The workflow for the design and implementation of such a program is described with a specific focus on four key requirements: 1) measurements must be on representative rock samples (the right samples); 2) measurements must be made under conditions representative of displacement processes in the reservoir (the right conditions); 3) measurements must be made using precision equipment and techniques (the right equipment); and 4) trained and experienced technologists are needed to conduct the measurements and model the data (the right people). The scope of the study was unprecedented in size in order to provide sufficient SCAL data coverage for the major static reservoir rock types (SRRTs), wide range of saturation conditions, different fluid systems (water-oil and immiscible gas-oil), as well as recovery processes (drainage and imbibition) encountered in the reservoir. Early engagement between engineering and geoscience disciplines ensured optimized coring and plugging practices for obtaining representative SCAL samples. In particular, a unique twin sample plugging and companion plug rock typing strategy was employed prior to SCAL measurements and was proven to be essential in enforcing accurate and consistent rock type assignment throughout the multi-year program. Continuous alignment with business functions also encouraged program optimizations that better address business needs. Overburden centrifuge capillary pressure and steady-state relative permeability results on native state samples are presented to demonstrate the high consistency and quality of data obtained from a well designed and executed SCAL program. The general trends observed from this expansive dataset, combined with recent advances in carbonate pore system characterization research, have yielded valuable insights into displacement behavior in heterogeneous carbonate rocks. The significant impact of high quality SCAL data on effective reservoir management is also discussed.
Study on Permeability Anisotropy in Carbonate Reservoir Samples Using Digital Rock Physics
Authors: Sun Huafeng , Vega Sandra , Tao Guo
Published: November 2015

Carbonate reservoirs can be extremely complex when estimating oil and gas production due to their texture heterogeneity, mainly from the structure of the pore space. Understanding the flow mechanism in carbonate reservoirs is essential for successful hydrocarbon development and production. Permeability is an important parameter and plays a key role in enhancing production and recovery. However, usually permeability anisotropy is observed due to the deposition, diagenesis, and/or tectonic movements of the rock formations, which complicates the reservoir characterization and description.

The digital rock physics (DRP) following the computed tomography (CT) scan techniques has progressed at a rapid speed since the three dimensional (3D) pore geometry structure of reservoir rocks can be captured and visualized and it is able to compute core sample parameters (such as porosity and absolute permeability) from the digital image (Kalam et al. 2013). To better understand permeability anisotropy in core samples from a carbonate reservoir, some accurate methods in DRP are followed.

In this study, five digital rock samples were selected to do the simulation. For each digital rock sample, in order to reduce the computational cost, three cubic subsamples were selected respectively from the upper, middle, and lower part of whole core plug as digital rock models. Then, the porosity and the absolute permeabilities in three perpendicular directions were computed (one in the axial direction, z, and two, x and y, perpendicular to the axis) in each of these cubic subsamples using the parallel lattice Boltzmann method (PLBM) in the high-performance-computing-cluster (HPCC). The results show that: (1) All the calculated porosities of the subsamples are close to the experimental porosities; (2) the calculated permeabilities in z direction of representative subsamples (Kz) are all close to the experimental permeabilities in the axial direction; (3) for four samples, Kz is much higher than the permeabilities in x and y directions (Kx and Ky, respectively). In other words, both Kz/Ky and Kz/Kx are higher than 1, and Kx/Ky ratios are closer to 1; (4) for only one sample, both Kz/Kx and Kz/Ky are less than 1, which may be caused by some geological structures present in this sample (stylolite); (5) permeability anisotropy in these carbonate samples is clearly confirmed and quantified.
Successful ESP Operation ADCO - SHAH FIELD
Authors: Kannan Jawahar
Published: November 2015

Artificial lift ESP's were installed in ADCO SHAH Field in the year 1994 to enhance recovery and sustain production. As of September, 2015 Shah Field has a total of 60 oil producers with ESP's, mostly characterized by applications with high water cut and low intake pressures. Additional wells are being drilled to enhance production.

High water cut and low intake pressures possessed a challenge, resulting in premature ESP failures thus impacting field performance indicators and cost of work over for ESP replacement.

To overcome these challenges ADCO has adopted optimization strategy to enhance oil production in a mature field by understanding the ESP system & reservoir conditions as an integral unit.

Shah Field has achieved one of the highest ESP run life of more than 15 years (Well no Sy-32 still running) and 6 more wells operating beyond the MTTF indicator. The objective of this paper is to share ADCO's successful optimization strategy to increase ESP life.
Seismic Reservoir Quality Prediction, Khazzan Field, Oman
Authors: Chris Stiteler T. , Sullivan Claire , Kumar Dhananjay , Matthews Samuel , Al Jahdhami Nafa Humaid
Published: November 2015

We present a seismic analysis workflow to evaluate tight gas sandstone reservoirs from a case study of the Khazzan field Barik formation, which is currently under development. The work from this field is particularly important because seismic attributes are playing a critical role in optimization of the field plan, mainly by distinguishing areas of good productivity from poor productivity.

Our evaluation starts with conditioning the migrated seismic data for AVO (Amplitude Variation with Offset) by reducing noise, flattening gathers, balancing amplitude and spectral frequency, and creating intercept, gradient and angle stacks. At the same time, a seismic rock property study is conducted, integrating acoustic well logs, petrophysical analyses and core data to model possible outcomes, and design the offset porosity and lithology volumes from conditioned data.

Then numerous attribute maps are extracted from offset and stack data, including Extended Elastic Impedance maps from offset data and amplitude maps of various types from stacked data. Key attribute maps from stacked data include average amplitude from colored inversion and spectral decomposition over the reservoir time window. After these products are created, statistical comparisons are made between attribute extractions at well locations and porosity-height from petrophysical analyses of logs and core studies. Graphs, statistics and bubble maps of actual and predicted porosity-height are analyzed together to develop preferred predictions showing distribution of uncertainty over the area of interest.

As development of the field progresses, seismic predictions of reservoir quality evolve with new wells being drilled, seismic data being improved and seismic attributes being tested. Initial efforts have already led to the optimization of the drilling schedule by re-scheduling wells from poorer to better areas, and planning for pilot wells to test areas of uncertainty. This seismic analysis workflow aligns with our goal to determine the degree to which seismic can be used to predict reservoir quality and guide field development, when integrated with geology, petrophysics and production data.
Well Completion Challenges in an Extreme Environment: A Case Study of the Design, Material and Completion Equipment Selection Process for Extreme Environments
Authors: Singh Basant Kumar
Published: November 2015

Well completion design is critical for the life cycle of a well. This includes expected loads during drilling, production, and work overs as well as metallurgical compatibility with production fluids. Any failure in the completion has the potential to jeopardize well integrity, delay production and can potentially impact the economics of the field development plan. There are long term studies on reliability of specific type well completion equipment which includes over 30 years of operational experience for well systems. This has provided a comprehensive database on well completion equipment with thousands of well-years of production experience and downhole failures. However, no such data base is available for well completions with high Ni CRA metallurgy for high sour gas field development.

Al Hosn gas commenced development drilling in one of the Southwest sour gas field, located 180 km southwest of Abu Dhabi in 2011. Phase-1 gas wells were drilled and completed in December 2014. The well design is a single lateral, open hole reservoir completion, with the laterals being approximately up to 15,000ft long. The well test data and logs were used to establish some of the completion equipment design parameters including H2S 20–30%, CO2 8–12%, salinity 160,000–220,000 ppm, BHT 275 -325 deg F, FTHT 225–250 deg F.

This paper highlights the work that went into completion design as well as choosing the metallurgy, connections type, elastomers, and the completion components. In some cases, this was the first application of the equipment in such an extreme environment. The process for designing a completion with high Ni CRA Metallurgy included: 1) literature survey; 2) identifying the required standards & procedures; 3) selection of required CRA metallurgies for required grades based on standards; 4) CRA vendor prequalification; 5) validation of all CRA metallurgies by lab tests for required conditions; 6) selection of connections; 7) validation test for CRA connections; 8) input from other operators & equipment providers; 9) strict management of change process for any deviation from specifications; 10) third party QAQC during manufacturing and make up of sub-assemblies. The completion design integrity has been proven under flowing condition during the well cleanups and flow testing on Phase 1 wells.
Land Data FWI: Methods and Strategies
Authors: Zhang Wei , Dai Nanxun
Published: November 2015

There have long been attempts to apply Full Waveform Inversion (FWI) to land data sets because it has the potential to build higher-resolution velocity models compared to traditional ray-based model building techniches. However, several difficulties hinder the successful application of FWI to land data: cycle skipping, unreliable amplitudes, as well as source and receiver signature estimation. To address these issues, we have developed three new FWI methods: the Dual Frequency Phase Difference (DFPD) Laplace Fourier domain FWI, Surface Offset Gather Flattening (SOGF) Wave Equation Migration Velocity Analysis (WEMVA), and Seismic Reflection Slope FWI. The Dual Frequency Phase Difference (DFPD) Laplace-Fourier domain FWI greatly simplifies the input data and promises the global minimum, and thus, is ideal for initial velocity model building. The Surface Offset Gather Flattening (SOGF) WEMVA method aims at maximizing the flatness of surface offset gather, which is a better objective than maximizing the focus of subsurface time/spatial lagged gather in terms of handling models with large lateral change. The Seismic Reflection Slope FWI method is capable of identifying small velocity anomalies such as gas clouds and faults, thereby producing a higher-resolution velocity model. Three model data examples are used demonstrate the capability of our methods: first we use a simple two-layer model to demonstrate that the Dual-Frequency Phase Difference (DFPD) Laplace-Fourier domain FWI is indeed immune to cycle skipping; second we use a steep boundary model to demonstrate that our Surface Offset Gather Flattening WEMVA is efficient at handling models with large lateral velocity change; finally we use the BP 2004 benchmark model to demonstrate the Seismic Reflection Slope FWI method is capable of identifying small velocity anomalies. We also note that these three methods can be combined together to form a FWI based model building strategy that produces high-resolution velocity model for land data set. Two field data examples are used to illustrate the effectiveness of this model building strategy. First, we applied the strategy to a 2D field data set acquired in Inner Mongolia. Two starting models were used, one is a simple model converted from time domain RMS velocity, and the other is from the traditional ray based model building approach. For both cases, our strategy was able to greatly improve the velocity model and the migration image. The migration image starting from the traditional ray based model had a superior focus and better followed the geological setting, indicating that our FWI strategy is compatible with traditional method and that, in order to get the best possible result, one would use our strategy subsequent to utilizing the traditional method. We then demonstrated this by applying our refined workflow to a 3D field data set acquired in the Pre-Caspian Basin, Kazakhstan, producing a velocity model with an improved migration image, containing fine details such as faults and channels.
Development of a Sweep Pattern Map for a Giant Carbonate Reservoir
Authors: Igogo Arit , Nzimako Uzoamaka Audrey , Khan Sara Hasrat , Al Blooshi Mariam Yousif , Al Shabibi Tariq Ali
Published: November 2015

For giant fields where potentials exist for further oil development, producing companies often step up developmental activities by drilling infill wells and carrying out reservoir monitoring activities to maximize the economic ultimate recovery. This would entail identification of bypassed oil, thief zones, and EOR opportunities. To ensure success of any drilling program or EOR scheme, a good understanding of the sweep pattern of the reservoir is imperative.

This paper highlights the utilization and integration of static and dynamic data for the development of a sweep pattern map for a hydrocarbon reservoir.

To develop the sweep pattern map, the reservoir was discretized based on the development regions and characterized based on results from cased hole logs (RST, PLT), open hole logs well production and injection data. The sweep pattern map was then developed by integrating all the available data and using cross section analysis of wells in each region to define the drainage pattern in that region.

This sweep pattern map gave a clearer picture of the current fluid distribution in the reservoir and this was used in locating zones of bypassed oil, identifying and evaluating potential EOR pilot schemes. Finally, the sweep map was compared with the fluid distribution from the dynamic model and it was found to be consistent.
New Possibilities in Gas Explosion Blast Wave Risk Mitigation in Critical Infrastructure Buildings
Authors: Paappa J. , Ronkainen J.
Published: November 2015

One of the main safety issues incorporates the risk of gas explosion. Active safety measures have been developed to prevent the incidents from leading into gas explosions. Though progress has been made, high overpressures associated with the gas explosion have still remained challenging. Lack of feasible solutions to protect the building ventilation openings from overpressures higher than 0.3 bar (4.4 psi) have resulted in designers trying to cope with the risk with plant layout design and forcing safety specialists to accept the risk to a certain degree.

Advances in gas explosion simulation have made it notable that blast wave will enter the reinforced building even from a small opening in a wall, typically an air vent. Even placing the air vent outside the line of sight of the blast wave will not solve the problem due to complex propagation and reflection pattern of the blast wave. Also manifestation of high overpressures has become more evident.

This paper discusses the various new possibilities offered by blast protection products for higher than 0.3 bar overpressure and multiple consecutive explosions protection. Attention has been given to the protection of ventilation openings in buildings as sufficient mitigation of explosion risks is required in order to sustain the operability of critical functions in emergency.
Design and Implementation of Low Salinity Waterflood in a North African Brown Field
Authors: Callegaro Chiara , Bartosek Martin , Nobili Marianna , Masserano Franco , Pollero Marco , Baz Doaa Mousa , Kortam Mostafa Mahmoud
Published: November 2015

The whole industry seeks to extend the economic life of existing brown fields, due to the difficulty of discovering new giant assets. The efficiency of mature waterfloods may be drastically improved by means of new technologies in order to recover a significant amount of unswept oil. IOR and EOR processes were investigated to increase oil production in a giant brown field in North Africa, developed by means of peripheral sea water injection. Current water injection scheme shows not optimal sweep efficiency and moderate recovery factor due to geological heterogeneity and unfavorable mobility ratio. This work describes the efforts to maximize water injection efficiency by means of the combination of different IOR and EOR techniques with focus on low salinity water.

A dedicated plan to enhance water injection was implemented considering the following pilots: a) water conformance by Thermally Activated Particles (TAP) tested in 2009 and extension planned 2015; b) polymer flooding started in the second half of 2015; c) Low Salinity (LS) water flood planned for 2016. In addition, the combination of the above technologies is under study and will be further evaluated based on the results of pilots.

LS water benefits were investigated within a comprehensive EOR study. First, tertiary corefloods on porous media were performed, showing an evident EOR effect compared with sea water, in increasing the oil recovery up to 7%. Modeling and uncertainty quantification studies showed that LS water may have a significant potential and can be synergically combined with polymer injection to maximize production. A sequence of Single Well Chemical Tracer Tests (SWCTTs) was performed in the second half of 2014 to quickly evaluate LS performance at the well scale resolution. Cycles of injection, shut-in and production periods were performed on a selected well to measure the residual oil saturation (Sor) after sea water and LS water. Promising results were achieved for LS, showing a considerable reduction in residual oil, of about 5-11 saturation units (s.u.) compared to sea water. The SWCTTs were used as a powerful tool to achieve a quick EOR response and confirmed low salinity potential.

The next phase foresees an interwell pilot to test the technology at a larger scale, whose design is currently ongoing. Moreover, the opportunity to optimize the existing polymer injection in a Low Salinity Polymer (LSP) treatment is under study to increase production and reduce project costs.
Acid Systems and ICD Design Considerations For Stimulation
Authors: Edmonstone Graham , Jackson Alfred , Kofoed Curtis , Shuchart Chris , Troshko Andrey
Published: November 2015

The recent industry development of drilling ERD wells with horizontal laterals in the reservoir of 10,000 ft. or more has led to a greater use of passive flow control devices and swell packers to achieve the desired inflow or outflow profiles. Another desire is to perform stimulation treatments of the lateral especially in tight carbonate formations. However, such treatments can create high velocities through the Inflow Control Devices (ICDs) that inevitably leads to high turbulence and wall shear stress in the ICD which can cause severe erosion and corrosion of commonly used materials. There appears to be little experience and associated knowledge on corrosion mitigation to ensure ICD integrity after well stimulation.

This paper will attempt to address such concerns through:

Discussing and analysing ICD design considerations to avoid high corrosion areas and selection of high alloy materials to resist corrosion. Selection of appropriate acid system and method to prevent corrosion. Laboratory testing of acid formulations under high wall shear conditions as predicted from Computational Fluid Dynamics (CFD) of the ICD design at reservoir conditions. Laboratory measurements of the performance of corrosion protection additives in acid formulations under wall shear conditions. Other possible mitigation efforts to reduce the need for stimulation treatments.

Each of these factors presents limitations which either restricts the use of aggressive acid systems or requires alternative acid systems that can lead to increased treatment cost and/or sub-optimal stimulation of the reservoir through the ICDs.

This paper discusses one producing company's effort to systematically improve the overall performance of stimulation through ICDs while maintaining the integrity of the lower completion liner.
Quality Assurance and Control of Surfactants for Field Scale EOR Pilot Projects
Authors: Barnes J. R. , van Batenburg D. W. , Faber M. J. , van Rijn C. H. , Geib S. , van Kuijk S. R. , Perez Regalado D. , King T. E. , Doll M. J. , Pretzer L. E.
Published: November 2015

Alkaline Surfactant Polymer (ASP) flooding is an enhanced oil recovery (EOR) technique that involves the injection of a solution of surfactant, alkaline, and polymer into an oil reservoir to mobilize and produce the remaining oil. There are several pattern-flood pilots in progress or about to be executed to evaluate ASP at a scale relevant to commercial scale application. The quantities of surfactants needed for these pilots and potential future commercial scale applications are large (100s to 10,000s of ton) and necessitate large scale manufacture using existing processes and plants for the different manufacturing steps. These operate under slightly different process conditions than those used to make the smaller quantity (ca. 50 kg) of the reference blend, used to design the formulation in the laboratory. The upscaling of the surfactant production itself is an essential step to enable field scale implementation of ASP. In order to ensure and control the quality of the surfactants produced for pilots with Shell interests, a stage gated Quality Assurance/Control (QA/QC) programme was designed and executed. The application of the QA/QC process for a high and a low active matter surfactant blend concentrate (around 60% and 20% active, respectively) is used to illustrate the process.

The early definition of the QA/QC programme provided a framework with clearly defined stages for upscaling from laboratory to large scale production. The definition of analytical and performance based laboratory experiments with up front defined specifications (minimum and maximum values) and repeatability allowed for clear, unambiguous decisions. Correlations between composition and performance that were developed based on pilot scale production were essential to assure the performance of the larger scale production. Core floods, used as the ultimate performance check, showed virtually identical performance for pilot scale prepared surfactants and surfactants from different large scale batches.

The paper illustrates that consistent industrial scale production of surfactants for application in chemical EOR is feasible. To ensure the quality of such surfactants requires a detailed QA/QC programme. The successful execution of the QA/QC programme for the surfactants for the pattern pilots ensures that the produced large scale surfactant blend performs as the reference blend used to design the formulation.
Chloride Stress Corrosion Cracking (Cl-SCC) of Stainless Steel Piping and Equipment in Condensate Stabilization Unit
Authors: Choudhary Satish
Published: November 2015

The purpose of this paper is to present a condensed summary of the work done by Dolphin Energy on chloride stress corrosion cracking (Cl-SCC). Stress corrosion cracking poses a serious threat to the integrity of a natural gas plant and the company responded to this threat by launching a comprehensive initiative to determine the cause(s) and to adopt best practices for preventing future failures.

This paper provides a valuable engineering insight into the ways and means adopted by the company for tackling Chloride Stress Corrosion Cracking issues in an operational plant without jeopardizing safety while maintaining the production targets at the same time. Included in this paper are various monitoring tools as well as interim and permanent preventive measures that were employed by Dolphin Energy following the first reported instance of chloride cracking in one of the stainless steel pipe works carrying hydrocarbon mixed with H2S.

One of the sources of the chlorides responsible for the corrosion/cracking failures was believed to be from hydrolysis of Ca/Mg/Na chloride salts generated in the hot stabilizer bottom and/or from left over hydrochloric acid (from well stimulations) in the well head production fluid. This condition was not considered during the design phase.

Interim and permanent preventive measures were identified for tackling the Cl-SCC issues. Key recommendations to address Cl-SCC included a reduction in operating pressure / temperature at vulnerable sections of the unit, use of various non-destructive testing (NDT) techniques to identify and monitor the cracks and generation of an Integrity Operating Window (IOW) to keep the key operating parameters within thresholds. It was determined that a material upgrade was the permanent solution for avoiding Cl-SCC in the Condensate Stabilization Unit.

A metallurgical investigation confirmed the mode of cracking to be intergranular as well as transgranular unlike conventional chloride cracking, which is primarily transgranular in nature. The reasons for observed mixed-mode cracking could be ascribed to certain combination of Chlorides, H2S, CO2 and partially oxidized sulfur species that are present in the service apart from the degree of cold work that material has undergone during fabrication.

It is important that within one year of commissioning the unit, a detailed review is made to verify process and operating parameters (design assumption versus actual operating conditions).
The Key Factors Affecting the Deliverability and OGIP of Multi-layer Gas Reservoirs
Authors: Yujin Wan , Yong Hu
Published: November 2015

For multi-layer gas reservoirs, the dynamic performance, especially the deliverability and OGIP (Original Gas In Place) of comingled gas wells, is seriously affected by the interlayer heterogeneity. The gas well production rate, if we set it as (1/3 to 1/5) of the absolute open flow potential (AOFP) by empirical method, will decline soon. There exists obvious difference between the OGIP, calculated by using the early period of production data, and the volumetric reserves. By integrating the experimental tests, gas reservoir engineering investigation and typical well dynamic performance analysis. Firstly, the experimental test of two parallel sets of full diameter core samples was carried out to simulate two-layer comingled producing, and the results show that the higher permeability layer produced more gas and its pressure decreased more quickly. Secondly, well test design model is used to simulate the dynamic performance of single layer and two-layer comingled wells, and the AOFP and OGIP calculated by the simulated results has been investigated. Finally, the dynamic performance of typical multi-layer comingled gas wells in Sebei gas field has been analyzed. The results of above all show us, the AOFP of comingled gas wells is mainly dominated by the higher permeability layer, the interlayer permeability differential and the layered reserves are the key factors to affect the AOFP and OGIP of comingled gas reservoirs.
Enhancements in Modeling Gas Sweetening
Authors: Sheikh Saifuddin
Published: November 2015

Acid gas removal is an important process in various branches of the hydrocarbon processing industry, primarily in natural gas processing and refining. Acid gas removal is also an essential part of other processes, such as coal gasification where carbon dioxide, hydrogen sulfide, carbonyl sulfides, mercaptans, and other contaminants need to be removed.

Acid gas is defined as gas containing significant amounts of contaminants, such as hydrogen sulfide (H2S), carbon dioxide (CO2), and other acidic gases. Sour gas is gas contaminated with H2S. This term comes from the rotten smell due to sulfur content. Thus, "gas sweetening" refers to H2S removal, because it improves the odor of the gas being processed, while "acid gas removal" refers to the removal of both CO2 and H2S.

Acid gases need to be removed in order to comply with sales gas quality regulations. These regulations are in place to minimize environmental impact and ensure gas transport pipeline integrity, avoiding undesired occurrences, such as corrosion caused by H2S and CO2 in the presence of water. Acid gases also need to be removed due to the toxicity of compounds, such as H2S, and the lack of the heating value of CO2. Typically, "pipeline quality" or sales gas is required to be sweetened to contain concentrations of H2S that's no more than 4 parts per million (ppm), and a heating value of no less than 920 to 1150 Btu/SCF, depending on the final consumer requirements.
Corrosion Under Insulation Technologies - High Performance Solutions
Authors: Pedersen Lars Thorslund
Published: November 2015

It has been recognized by most facility owners that corrosion under insulation is a phenomena which needs special attention during design and construction. If the pipes and vessels are left uncoated or if the wrong type of coating has been applied before the insulation material is wrapped around – the result will often show up in a few year times in form of heavy corrosion under the insulation material or even break down due to leaking pipes or vessels.

Selecting the correct coating to protect the vessel or pipe before insulation can be a challenge especially when we see a lot of new coating technologies reaching the market. This paper will discuss the reason for have different coating technologies available and what to look for when specifying coatings under insulation.
Application of CO2 Micro Bubble for the Innovative CO2-EOR
Authors: Akai Takashi , Xue Ziqiu , Yamashita Yuji , Yoshizawa Minoru
Published: November 2015

CO2-EOR is one of the proven enhanced oil recovery (EOR) techniques and has been used commercially. However, in field applications, unfavorable sweep efficiency is often reported. In order to improve the sweep efficiency of CO2 flooding, we investigated an applicability of CO2 micro bubbles.

To evaluate the applicability of CO2 micro bubbles for CO2-EOR, we conducted core flooding experiments using CO2 micro bubbles and the results were compared with the normal CO2 flooding. Previous study confirmed the generation of CO2 micro bubbles by using a specially developed porous filter. Using this filter, core flooding experiments were conducted. During the experiment, flooding behavior was monitored by a medical X ray CT system, and recovered oil and water were collected to make a quantitative comparison with normal CO2 flooding.

From the images taken by the medical X ray CT, we observed that CO2 micro bubbles flowed over both upper and lower parts of core samples, while normal CO2 flowed only upper part of core samples. As a result, a delay of CO2 break-through was confirmed in CO2 micro bubble flooding case. The time series of medical X ray CT images indicates improvement in sweep efficiency by using the CO2 micro bubbles. In addition to this, the material balance calculation during the core floodings revealed 3% of additional oil recovery compared to the normal CO2 flooding. From the experiments, differences in flooding behavior were clearly observed between the normal CO2 and the CO2 micro bubbles injection. We consider the differences would lead to the improvement of both vertical and areal sweep efficiencies.

Although this technique is still in a stage of fundamental research, since the technique only requires the special filter and it is considered that it can be easily installed at the down hole, it may provide a novel option to improve the CO2-EOR performance.
Consideration on Shape of Hydraulic Fracture Based on Laboratory Experiment
Authors: Akai Takashi , Yano Shunsuke , Kurosawa Isao , Chen Youqing , Ishida Tsuyoshi
Published: November 2015

In development of unconventional reservoirs such as tight and shale oil/gas reservoirs, hydraulic fracturing has been applied to enhance reservoir productivity. In spite of active applications of hydraulic fracturing, a shape of induced fractures is not fully understood. This paper presents the result of laboratory visualization experiment of hydraulic fracturing, which was conducted to visualize the shape of induced factures with cylindrical shale sample through the fluorescent method. An acrylic resin mixed with a fluorescent agent was used as a fracturing fluid. The resin is solidified and fixed within the samples by heat. The shape of the induced facture reveals based on different brightness under ultraviolet light irradiation. Many associated microfractures were observed around the main fractures. The fracturing fluid can be trapped in these types of microfractures by capillary force and these fractures cause lower recovery of fracturing fluid in the actual field operations. Acoustic emission (AE) was also monitored by the 16 sensors mounted the rock samples. Result from the path of main fractures identified by the resin mixed with a fluorescent substance and distribution of AE indicates good agreement between two. This helps us to examine which particular failure generates microseismicity. Although the scale difference between laboratory experiments and field operations needs to be taken into account, the shape of induced fractures is successfully characterized. We interpret the fluid leak off zone, main fracture, and branch fractures can be a source of the AE while no AE is observed at the area of the fracture with large aperature based on overlaying AE hypocenters with visualized induced fracture. This work helps engineers to make a proper model of hydraulic fractures for the estimation of well productivity.
Enhanced Security for Oil and Gas Facilities in a Volatile World
Authors: Aspden Albert
Published: November 2015

Oil and gas facilities are usually situated in remote locations. These areas are often geo-politically sensitive areas, with infrastucture that has little, if any, protection.

Nonetheless, these facilities often represent several billions of dollars of an investment portfolio, making them high in both monetary and strategic value, and at risk of sabotage or attack..

A client requested a solution to provide protection systems for a vast gas field from such malicious threats. The objective was to design a system that would: DETECT a potential threat;ASSESS the threat (friend or foe);ACT on the threat

This paper discusses the technology options considered and the prescribed solution: Using access control systems and closed-circuit television (CCTV) surveillance to protect numerous facilities and major gas pipelines across a geographic area of some 1,300 square km.
Integration of Evolving Petrophysical and Formation Testing Measurements for Enhanced Characterization of Tight Gas Reservoirs
Authors: Mohsin Labib , Sassi Khaled H. , Yaarubi Azzan H. , Daungkaew Saifon , Yu Dai G. , Lawatia Redha H.
Published: November 2015

Tight unconventional reservoirs have become an increasingly common target for hydrocarbon production in Oman. Exploitation of these resources requires a comprehensive reservoir description and a characterization program to estimate reserves, identify properties that control production, and account for fracturability. It is becoming evident, however, that any single technology by itself is unable to address all the key challenges, and the integration of technologies is crucial to answer all the questions to reduce key subsurface uncertainties.

This paper discusses in detail a case study in which the integration of advanced petrophysical logs has enabled successful downhole sampling and provided a comprehensive reservoir and fluid characterization despite the very challenging lithologies and very tight formation. The comprehensive logging suite included advanced measurements of dielectric dispersion, nuclear magnetic resonance (NMR), and spectroscopy. The reservoir fluids and dynamic properties were also characterized by a series of formation testing measurements.

Dielectric dispersion logs clearly identified the hydrocarbon-bearing zones despite the characterless resistivity profile, taking advantage of its resistivity-independent saturation approach. The accuracy of the measurement was key to estimating water- filled porosity down to 0.5 p.u. regardless of the formation water salinity and changes in the rock electrical parameters. The integration of dielectric and NMR measurements, reflecting the pore structure, has played a major role in identifying the "best" reservoir intervals and indicating the type of fluid (hydrocarbon or water) filling the free pore space. The NMR unimodal and bimodal T2 distributions revealed the pore structure along with polarization effects on light hydrocarbons, helping to gain insight on the reservoir quality. The NMR was also combined with the microimaging measurements to indicate pore connectivity and formation heterogeneity. This integrated approach was applied to a deep tight-gas exploration well and has contributed to achieving successful formation sampling that provided an in-situ fluid characterization despite the tightness of the rocks, with only 4 p.u. average porosity. Integrated logging measurements along with fluid sampling resulted in both enhanced formation and fluid characterization in this exploratory well, shedding light on the hydrocarbon potential over the region.
Improvement of the Compositional Model to Represent a Complex Fluid System of a UAE Carbonate Reservoir
Authors: Alejandra Khan Karem , Uchida Miho , Noah Awolayo Adedapo , Olawale Olayiwola Saheed , Al Hammadi Khaled Eissa
Published: November 2015

The studied field is located in Abu Dhabi and has been identified as faulted anticlines structure with associated local fractures. The reservoir is characterized by lateral and vertical variations in reservoir rock and fluid properties ranging from a gas condensate at the top of the structure to undersaturated black oil down the reservoir. A substantial compositional gradient has been identified from over 50 fluid samples taken at different depths over the thick fluid column of about 1500 feet. The field is presently under miscible hydrocarbon WAG (HC-WAG) injection, water injection and future consideration for CO2-WAG injection.

The field has been characterized using an Equation of State (EOS) model and compositional mapping with areal changes of saturation pressure. Therefore, the aim of this study is to improve the compositional model that can replicate the areal and vertical variation in the fluid thermodynamic. This presents a huge task considering the vast number of laboratory experiments. Hence, the updated EOS will be used to improve the reliability of reservoir modeling, production forecasts and operational requirements.

All the fluids analyses studies were compiled and validated. These data were analyzed areally and vertically down the fluid column. Correlations of saturation pressure, gas-oil ratio, formation volume factor and compositions were generated with depths across the formation. The data showed a large variation of saturation pressure, all fluids parameters and composition with depth especially close to the gas oil contact. Then the compositions and saturation pressures were validated using a 1-D vertical model and obtained results were compared with the experimental values at various depth.

The obtained result proved that a single EOS and fluid representation could model the complex thermodynamic behavior of all the reservoirs in the field. Considering that part of the field has been under HC-WAG injection and future consideration for other WAG processes, the generated EOS would allow the numerical simulation to have a better representation of the fluids and predict the impact of these processes on the ultimate oil recovery.