bluuebunny/crossref_metadata_2025 huggingface dataset:
Dual Role of Citric Acid as a Binding Inhibitor of Anionic Surfactant with Bivalent Cations and Co-Surfactant on Bio-Surfactant EOR
Authors: Miyazaki Nao , Sugai Yuichi , Sasaki Kyuro , Okamoto Yoshifumi , Ouyang Chencan
Published: November 2018

Surfactin is an anionic surfactant generated by bacteria. Although it has high ability to decrease interfacial tension (IFT) between oil and water, it binds with bivalent cations and forms precipitation. Because the precipitation causes the significant reduction of reservoir permeability, surfactin cannot be applied to EOR in oil reservoir whose bivalent cations concentration is more than 100 ppm. This study investigated methods for applying surfactin to reservoir containing bivalent cations with high concentration.

Screening of an effective binding inhibitor was carried out by measuring turbidity of the solution containing 0.3 wt% of surfactin, 900 ppm of calcium ion, and inhibitor candidates such as alcohols, chelating agents, cationic surfactants, and ion capturing substances. Influence of the inhibitors on surfactin capacity for decreasing IFT was also evaluated by measuring IFT between the solution and oil. The best inhibitor was finally selected through the injectivity tests using Berea sandstone core which was saturated with calcium solution. EOR potential of the solution containing the inhibitor was evaluated by the core flooding experiments.

Citric acid and trisodium citrate inhibited binding of surfactin with calcium ion with lower concentration such as 0.6 wt%, they were selected as potential inhibitors and subjected to the IFT measurements. Both of them had strong potential as co-surfactants of the surfactin because IFT was greatly decreased to less than 0.1 mN/m which was less than a tenth as compared with IFT between the pure surfactin solution and oil. Trisodium citrate however caused significant permeability reduction on the injectivity tests whereas citric acid could be injected into the core without permeability reduction. The high pH value of trisodium citrate solution might cause the dissolution of ferrum and aluminum in the core and the colloids of ferrous hydroxide and aluminum hydroxide were formed in the core, which brought the significant permeability reduction. Citric acid was selected as the best inhibitor and subjected to the core flooding experiments. 25 % of oil remaining after primary recovery was recovered by injecting the solution containing 0.3 wt% of surfactin, 0.6 wt% of citric acid and 900 ppm of calcium ion. Rise in the differential pressure was not found during the injection of the solution, which suggested that citric acid was effective for inhibiting the precipitation in oil reservoir. Moreover, 25 % of recovery factor was 5 % higher than the recovery factor obtained by injecting pure surfactin solution. Citric acid is also effective for enhancing the surfactin capacity for increasing the recovery factor.

Citric acid has dual role as the binding inhibitor and co-surfactant. Because citric acid is environmentally friendly and cheap chemical, it can be promising additive which increase the applicable reservoir and potential of surfactant EOR.
New Borehole Image Log Based Technique for Pore System Characterization Predicts Productive Intervals in a Tight Carbonate Reservoir in Abu Dhabi
Authors: Noufal Abdelwahab , Obaid Khalid , Al Blooshi Abdulla , Nehaid Hani , Basioni Mahmoud , Alward Wassem , Uruzula Jaja , Shamsal Sudipan , Dasgupta Suvodip , Raina Ishan , Schlicht Peter
Published: November 2018

Carbonate reservoirs of the Middle East are known for exhibiting highly heterogenous nature in terms of reservoir properties within microscopic intervals of the reservoir, making it difficult to characterize and predict. An integrated approach involving detailed understanding of the fluids volumes porosity distributions, permeability systems, rock textures, reservoir rock types, and natural fracture distribution at different scales is needed. Accurate characterization for the flow networks, complicated by fracturing and diagenesis is fundamental to achieving realistic prediction, better production performance, and increased recovery. The rock texture in carbonate reservoirs is very unstable and continuously undergoing to multiple stages of dissolution, precipitation, and recrystallization, which obscures any relationships that might have existed between depositional attributes, porosity, and permeability. Fractures make it more complex with their different morphology, often further convoluted by leaching through them. Different measurements are needed to build a realistic model of the petrophysical properties of a carbonate formation. The standard resistivity and porosity measurements are often not sufficient to resolve changes in pore size and texture, so additional measurements are required. Workflows using borehole images can be used to extract information on different textural elements and porosity types. With the newly introduced workflow secondary porosity types are distinguished from matrix porosity and proxies for permeability are calculated.

This workflow integrates borehole images and other petrophysical data in sequential steps and provides important reservoir parameters. With the suggested analytical workflow, it is possible to classify the different types of pore space such as connected to vugs (vug to vug), isolated, connected to fractures, aligned at bed boundaries, or within the rock matrix. The contribution of these different pore types to the total porosity of the formation is quantified in addition to the geometric information of different types of heterogeneities. In addition, the connectedness of the different types of porosity is quantified. The connectedness log describes the quantity of connected spots detected from the electrical borehole image and is used as a predictive measure for identifying zones of higher or lower permeability. During operation it serves as an indicator for determining the perforation intervals, in static reservoir modeling it serves as a permeability driver to improve reservoir mapping. We demonstrate an example where the connectedness successfully predicted productive zones, proven by production logging.
Pre-Magnetization of Transformers
Authors: Abouelmakarem Mohamed , Kotrappa Murugendrappa , Al Ammari Sara , Manna Malay , Santhanamuthu Thenarasu , Sundaresan Hemachandran
Published: November 2018

Power supply in Oil & Gas offshore fields is very important to ensure production continuity; Pre-magnetization Transformers were introduced to avoid/reduce serious disturbances and voltage dips that may lead to blackouts when switching on Transformers at random instants.

Power transformers are generally energized by closing the circuit breaker at random instants. Consequently, the voltage of the supply system is also applied on the transformer windings at random instants. This switching usually introduces an asymmetrical magnetic flux in the windings that can drive the transformer into saturation. As a result, transient magnetizing inrush currents of high magnitude are generated in the transformer, which may cause serious disturbances leading sometimes into severe voltage dips or resulting in a complete blackout especially in weak grids such as remote offshore power networks.

With reference to figure 1 (Gonzalez et al, 2016), it can be seen that the worst case scenario would during close the circuit breaker at zero voltage level. This will cause the flux to peak up 2 times its normal operation causing the saturation of the core and asymmetrical inrush currents. Point on Wave controllers may be used to limit these effects. Figure 1Energization of Transformer at Worst Case Scenario

The design and installation of the Pre-magnetization transformers are described in this paper. One of the solutions for mitigating the high inrush current is to construct LV pre-magnetizing winding in the power transformers. This system involves initial energization of transformer core through LV pre-magnetizing transformer prior to connection of transformer primary to the main bus. This has the effect of pre-magnetizing the transformer’s core and aligning magnetic fields so that inrush is negligible when the primary feeder breaker is closed.

After careful evaluation of other technologies available like Point on Wave switching techniques … etc; Pre-magnetization of transformers is found to be highly secured solution which avoids all uncertainties due to critical nature of Oil & Gas Offshore Power networks.

A preliminary study has been done by using ETAP. This study clearly illustrated that electrical voltage drop is within the acceptable range after implementation of pre-magnetization transformer.

This paper describes the solution which was introduced for the first time in many different locations like natural islands, artificial island and Offshore Oil and gas Super Complex with integrated 132kV Subsea Power network. Rather than causing serious disturbances and voltage dips, this solution can be implemented in weak power grids to improve system stability.
Quantifying the Non-Monotonic Effect of Salinity on Water-in-Oil Emulsions towards a Better Understanding of Low-Salinity-Water/Oil/Rock Interactions
Authors: Gomez Sergio , Mansi Mohamed , Fahes Mashhad
Published: November 2018

Low-salinity water injection for EOR applications and for shale and tight sand fracturing has become a widely accepted approach. Experimental and modeling work is slowly unraveling the complexity of this system, with no unified theory to explain the fundamentals behind it. Our work adds a new spin to the topic, where the non-monotonic impact of salinity on contact angle reported in literature is linked to its non-monotonic impact on the properties of the water-oil interface.

We used a crude oil sample that originated from a field in Texas to create surfactant-stabilized brine-in-oil emulsions. We synthesized different brine systems starting from deionized water using two different salts, NaCl and CaCl2 at 8.55, 85.5 and 855 mMol/L. We quantified the stability of the emulsion using both gravimetric and centrifuge methods. We measured the variation in the viscosity of the emulsion for different brine fractions from 10 to 50 wt%.

The results show a different effect of salt on stability for different values of water-cut. This effect can range from a stability being directly proportional to salt concentration in one case, to being inversely proportional to salt concentration in the other case, including a scenario where a non-monotonic impact is recorded.

The work provides a comprehensive and detailed set of experiments on various measurements relating to the brine-oil interactions away from the influence of rock minerals. It shows similar trends to what is reported in the literature on experiments and simulations where carbonate and sandstone rock minerals are included. This brings to question some of the theories that are used to explain this behavior given that the complexity is evident even without the rock presence.
Alternative Operation Scheme for a Jackup Drilling Rig to Meet Target Soil Bearing Pressure Requirements
Authors: Beebe Tony , Vazquez Jose H. , Rousseau Joseph , Samuelsson Lars , Cunnion Pete , Coan Clay
Published: November 2018

The goal is to define conditions under which a GustoMSC CJ46-X100-D jackup rig designed for unrestricted service can be rated for full operational drilling capabilities in areas with a relatively weak soil top layer and a more benign environment. The GustoMSC CJ46-X100-D jackup rig is designed with environmental criteria derived from the southern North Sea and a bearing pressure of 53.5 MT/m2 (10.96 ksf); however, the maximum soil bearing pressure in some areas of the Arabian Gulf and elsewhere cannot exceed 41.5 MT/m2 (8.5 ksf).
Brownfield Survey Techniques Training and Development
Authors: Watson Kevin
Published: November 2018

An offshore survey is one of the key aspects in ensuring the successful implementation of any Brownfield project scope. When there are shortfalls in the offshore survey process, it can often lead to re-work offshore typically resulting in a substantial impact on costs and schedule.

For many years now, experts have predicted about extensive opportunities for Brownfield Projects in the Middle East (The Middle East Brownfield Projects Conference), sharing insights and strategies to rehabilitate mature, aged fields and depletion of well pressures. Clearly defines the Middle East's brownfield market as one of the region's high potential markets.

Oil & Gas Companies are fully aware of this and are constantly seeking effective, innovative, less complex ways to extend the lives of their existing facilities. Additionally, with oil prices falling to around $50 a barrel and with world vulnerability across the industry, our clients are under pressure to keep downtime to a minimum.
Permeability Derivation from Sonic Stoneley Wave Attenuation Measurements: Application in a Giant Carbonate Field from Middle East
Authors: Yin Hezhu , Wu Xianyun , Yose Lyndon
Published: November 2018

Permeability is one of the most important parameters that is required in reservoir simulation, field development, and reservoir management. An innovative permeability derivation method and workflow has been developed using Stoneley wave attenuation mechanism (not Stoneley wave velocity as discussed in some previous studies). The workflow was applied to the sonic waveform data acquired from a vertical well in a giant carbonate field in Middle East. The workflow includes (a) extraction of Stoneley-wave attenuation rigorously from the waveform data, and (b) fast inversion from Stoneley-wave attenuation to permeability.

Validation of the method and workflow were performed by comparing the results with core permeability and MDT mobility data. Results from this application indicate that low-frequency monopole waveforms provide good quality Stoneley wave data, and that Stoneley wave attenuation responds to permeability changes. The Stoneley-wave attenuation log extracted from the low-frequency monopole waveforms shows variability, and the permeability log obtained using the inversion workflow through different reservoir intervals has a good overall correlation with core permeability. The main reservoir interval is over 100 feet thick. Porosities are generally high throughout the interval, but permeabilities vary by several orders of magnitude due to pore type changes. The Stoneley wave attenuation permeability trend corresponds very well to vertical changes in the dominant pore system. Stoneley-derived permeabilities distinguish between microporosity in lower section with permeabilities in 1-20 millidarcy range, and mixed-pores in the upper section with permeabilities in the 10's to 100's of millidarcy range. The sonic permeability is also picking up tight streaks (stylolite zones with cementation) that have low porosity and permeability and can act as flow baffles within the reservoir. These results show that Stoneley wave attenuation is responding to changes in carbonate pore systems, and that Stoneley-derived permeabilities can provide useful permeability estimates in the absence of core data.
Engineered Flexible Expandable High-Density Cement System in Loss Prone High-Pressure Salt Section in Northern UAE
Authors: Sales da Silva Aguida , Schebath Dominique , Phyoe Thein Zaw , Kapoor Saurabh , Herrera Albuja Eduardo , Sajid Muhammad
Published: November 2018

The objective of a cementing operation is to achieve a long-term well integrity by providing good zonal isolation. In cementing operations in the northern part of the United Arab Emirates (UAE), thick salt formations, potential high-pressure zones, lost circulation zones and planned high pressure casing test added to the complexity of the cement job.

The presence of 3,000-ft or thicker salt formation posed a key challenge. The chemically reactive salts in the salt sections affects slurry placement and hydration. Salt from formation can be incorporated into cement slurry while placement and adversely affects the fluid loss, rheology, and setting characteristics. Thus, first, the cement system needed to be designed to be tolerant of such effects. Also, high pore pressure was expected while drilling so the planned mud density varied from 15.5 ppg to 18 ppg. The highest cement slurry density of 19.2 ppg was required to cover this wide range while maintaining the density hierarchy requirement for optimum placement. Additionally, a high-pressure test planned after the casing was set resulted in additional stresses, which also posed substantial risks to the integrity of the cement sheath.

A methodical approach was applied by first following the standard cementing practices and then categorizing the key factors in overcoming field specific challenges. Stress analysis using advanced software helped to identify the needed mechanical properties for the flexible and expanding cement system to remain intact under extreme pressure changes. After the in-depth lab testing, a fit for purpose compatible for placement against salt formation cement system was introduced. The use of engineered lost circulation fibers in the cement system would help to mitigate the losses during the cement job.

The engineered high-density salt compatible flexible expandable cement system was designed to provide the desirable outcome to the complex challenges. Comprehensive lab testing along advanced zonal isolation software helped in successful first-time execution.

The first-time application of this salt compatible flexible and expanding cement system has proven to be a robust solution for the cementation and could be the basis of design for all future wells industry-wide.
Integrating Real-Time Azimuthal Acoustic Data with Wellbore Stability Analysis for Safe and Fast Drilling, South & East Field, Kuwait
Authors: Belhouchet Mohamed , Al-Turkey Shaikha , Shah Bora Mir Alam , Al-Hindi Khaled , Al-Failakawi Fatma , Nair Abhilash , Elabsy Islam Mohamed , Abdessalem Abba
Published: November 2018

Before a well is drilled, the forces and stresses acting within a formation are in equilibrium. However, as the wellbore is drilled and a cylindrical volume of rock is removed, the stresses originally exerted on that volume must instead be transferred to the surrounding formation. The cylinder of rock is essentially replaced by a cylinder of drilling fluid, with its hydraulic pressure substituting for the mechanical support of the rock being removed. The hydrostatic pressure from the drilling fluid is uniform in all directions, and it cannot replicate any directional shear stresses that exist within the formation.

Formation stresses redistribute around the borehole wall, and if they exceed the rock strength, the borehole will start to deform. If the borehole wall itself begins to fail, the resulting problems could include stuck pipe, borehole wall breakout, swelling shales, and unintentional hydraulic fracturing.

The ability to predict and implement corrective action prior to any borehole problem occurring greatly reduces operational risk and ultimately increases operational efficiency. This is accomplished through the development of a geomechanical model which combines local geological and geomechanical field knowledge with comprehensive drilling and evaluation data from offset wells.

The geomechanical model provides the ability to predict and simulate wellbore stability of a planned well. Fields exhibiting considerable lateral heterogeneity and depositional variation can be challenging, but prediction and planning become more accurate as additional wells are drilled.

The well discussed in this paper was drilled with a bottomhole assembly (BHA) which included an azimuthal acoustic tool that enabled real-time wellbore stability analysis and equivalent circulating density (ECD) measurements to maintain an accurate mud-weight window. Real-time monitoring allowed predicted model responses to be confirmed, and/or the model to be updated.

The well was drilled to its final depth with no adverse borehole events, resulting in a quality borehole and a casing run with zero nonproductive time (NPT).
On the Pressure Response During Unsteady State Fluid Displacement Experiments
Authors: Mehana Mohamed , Fahes Mashhad
Published: November 2018

The pressure response observed during the unsteady state displacement is a critical factor in determining the steady value and contains valuable characteristics about the rock permeability and capillary pressure. Our objective is to elucidate the mechanism of the unsteady state displcment and its impact on the pressure reponse. We tried to match the experimentally-measured pressure profile using both numerical simulation and analytical solutions. Promising results are observed when the capillary pressure is considered. The results clarify that this response is not a function of gas compressibility or viscous fingering, but is directly linked to the ratio of liquid fractional flow to liquid relative permeability as a function of saturation. The relative permeability exponents have a direct role to play in this regard. This work highlights the inacpaibility observed in a reservoir simulator to capture the pressure signature. This brings into question the ability of such simulators to provide reliable data when it comes to model the displacement processes at the core-scale.
Electrification of Oil & Gas Offshore Installations with HVDC Submarine Cables
Authors: Toulotte Maxime , Lervik Lars , Renaudin Fabien
Published: November 2018

Electrification of Oil & Gas offshore installations can be performed by transmitting electrical energy over long length using high voltage direct current (HVDC) submarine cable systems. This paper describes the two commonly used technologies for HVDC submarine cable systems and the current state of the art. A technico-economical analysis has been performed for the supply and installation of an HVDC submarine cable system located in the Middle East, which shows that cable loss valuation should be considered together with the technology readiness level (TRL), in addition to the initial investment cost. Depending the voltage level, cross-linked polyethylene (XLPE) cables have a lower investment cost than mass impregnated (MI) cables, but considering the loss valuation and TRL, MI cables could be preferred considering the cable system only. This study gives an input to the full project value of an HVDC transmission system, where cost and losses of converter stations for different technologies and at various voltage levels should also be included.
Faster Restoration of Wells Using HWOU Snubbing Unit
Authors: Narwal Tushar , Busaidi Asaad , Ghenaimi Habib , Oguni Blessing , Abri Zahir , Benchekor Ahmed , Hadhrami Abdullah
Published: November 2018

In south-eastern part of the Sultanate of Oman, PDO is producing from one of Tight Sour Field (with H2S 1-2%) with current reservoir pressures ranging from 40,000 to 60,000kpa for more than 20 yrs. Due to tight nature of reservoir, the wells are hydraulically fracced to produce, but with time the production rates decline and wells start to produce in unstable mode. This unstable production mode leads to huge scaling and corrosion issues which results in tubing failures requiring huge and expensive workover to restore well production. Due to low production rates and expensive workover makes these intervention very less attractive in terms of Net Present Value (NPV) compared to other opportunities.

This paper describes the challenges in restoring production from wells with tubing leaks using conventional workover techniques and the advantages of using new approach of using Hydraulic Work Over Unit (HWOU/Snubbing unit) to workover these wells.

Using HWOU for workover restoration time from the failure to restoring production has been reduced from ~2-3yrs to almost less than a year along with significant reduction in overall cost (more than 40% per well). This approach has been successfully applied to 2 wells till dates and upcoming workover will be done in similar manner.
Reduction of CAPEX for Offshore Platforms in Shallow Water Depth with Uncertain Reservoir Capacity by Adopting a Two-Phase Installation Approach
Authors: Chatterjee Prabir Kumar
Published: November 2018

Fixed Offshore Platforms (FOP) in shallow water depths for wellhead-cum-production operations are frequently installed by float-over deck technique to reduce offshore tie-in and commissioning time. Generally, float-over deck installation method is justified for a medium to reasonably large topside involving many equipment (related to process, electrical, instrumentation, utilities and HSE) and piping that can be pre-commissioned onshore to a large extent before sail-off. A high CAPEX for construction and installation of such platforms may be justified for a proven field in which reserve may last for several years with 8 or more numbers of drilled wells. However, when the reservoir volume and pressure is uncertain, the investment risk is too high to make a commercial decision for a medium to large sized offshore platform.

Whatever be the installation technique, structural design of an FOP is greatly influenced by the topsides requirements in terms of space and weights of various equipment/facilities to be supported and the construction/installation methods to be adopted. In the present study, structural design of an offshore wellhead-cum-production platform in 26m water depth is carried out considering a conventional but two-phase installation approach for the structure as well as the topside facilities. This approach for an oil production platform is suggested to reduce the high initial CAPEX when the expected success of drilling outcome is uncertain. The first phase will consist of only essential facilities such as power generation/supply unit, equipment for well testing, separation of water & gas from oil, heating unit in case of high viscosity crude and critical safety related equipment before sending the crude to onshore through pipeline. In case of successful drilling outcome and proven reserve, the offshore platform can be further extended (Phase-2) by installing remaining facilities such as installation of low pressure system, sand handling unit, artificial lift equipment, produced water treatment plant.

A comparison of structural weight and cost has been made between the proposed platform and an actual float-over platform of similar deck space. The advantages of the proposed design are (i) significant reduction of investment risk by lowering the initial cost and (ii) significant reduction of the overall structural weight resulting in cost saving for structural material and fabrication.

In spite of two-phase installation approach, the cost of conventional installation will be less than the float-over installation due to the requirement of smaller capacity crane vessel and less marine spread. Based on the results, it is found that a two-phase installation approach may govern the design for certain fields due to low initial cost and reduced overall cost of medium sized FOP's.
The Dichotomy of Lost Circulation Material – Is Their Application in Prolific and Troublesome Formations Mitigating Losses or Progressing as a Habitual Practice?
Authors: Bijjani Patrick , Anez Marcos , Luyster Mark , Tresco Kim , White Craig , Dobson Jay W.
Published: November 2018

A review of lost circulation plans, contingencies, recaps, and methods used to primarily prevent losses in the upper-hole sections drilled in the offshore region of the Arabian Gulf was compiled in an effort to ascertain which lost circulation treatments and/or combinations were historically effective or ineffective for regaining circulation especially after total losses, whereby total planned depth was achieved with little to nil non-productive time (NPT) as related to drilling fluids. This evaluation highlighted numerous inconsistencies and excessive time committed to combating losses whereby the critical path was marginalized. While these wells comprised sole objectives, their upper-hole sections were drilled through known troublesome formations often with the same result. It was surmised that the type of lost circulation material (LCM), combinations of LCM, and frequency of use contributed little to no benefit in particular circumstances. Subsequently, this review was undertaken to ascertain if time could be saved with more prudent utilization and/or tactics when utilizing LCM to combat losses.

A well-known application of LCM is its usage as background solids to mitigate fluid loss in troublesome wellbore sections primarily due to the relatively inexpensive cost, availability, ease of use, and compatibility with the drilling fluid. LCM are supplied in a myriad of sizes, types, textures, and applied in varying concentrations and combinations. This review details numerous LCM types and combinations in addition to various pills. While attempts were successful in stopping losses in the upper-hole sections, success was sometimes temporary as subsequent drilling operations would, in some cases, realize losses greater than the established trigger rate.

The ensuing discussion includes a synopsis of challenging vugular and/or fractured carbonate formations in the UAE and Copper Ridge Formation in the US, a review of common and some uncommon LCM, the field results, and finally, lessons learned and strategies are propositioned. The selected LCM are contrasted with their application in formations of the upper-hole sections versus various loss scenarios and results.
Heavy Lift Performance of Seven Champion Under Wave Conditions
Authors: Luong Tuyen , Kurundwade Santosh , Trisnawan Wahyudin
Published: November 2018

This study develops a numerical hydrodynamic model in time domain to simulate an offshore heavy lift installation of a topside by using the crane of a heavy lift vessel (HLV) – Seven Champion. The main purposes of this model are to understand the behavior of the vessel during the lifting installation, to determine operation weather windows and to optimize the installation procedure. A 3D hydrodynamic diffraction model of the vessel, lifting crane and topside with rigging system are simulated together as an integrated model in time domain by using MOSES software to study interaction between vessel motions and pendulum effects of the lifting system. Dynamic hook loads (DAF) are recorded and compared with established design criteria to ensure safety lifting operation and the numerical results are also compared with real offshore records during real heavy lift conditions. The studies show that the analysis results strongly depend on chosen mesh size and time step. Using an appropriate mesh size and time step and convergence study are important to ensure appropriate analysis results in time domain simulation. Various parameters of environmental conditions including wave heading angle – β, peak period - Tp and significant wave height Hs are investigated to define weather matrices and find out limiting operation windows. The obtained DAF can be used to compare with allowable DAF values to determine the weather window limit for the offshore lift operation. These studies showed that environmental conditions strongly affect HLV's lifting performance especially wave headings and peak periods. The simulation by using a numerical hydrodynamic model gives better prediction of HLV performance under heavy lift condition and comparison between numerical results and real offshore records help to give more confidence in design practice. From the analysis results, offshore contractors and client can develop optimal design solutions and good operation plan and schedule which are key points for safe and successful executing of an offshore heavy lift.
Gas Well Performance Analysis with Downhole Gas Compression
Authors: Montoya Cesar , AlAdawy Ahmed , Malkawi Ameen , Lastra Melo Rafael
Published: November 2018

Downhole gas compression is an artificial lift means that aims to increase production, maximize recovery and delay onset of liquid loading from gas wells. Being a technology not widely implemented yet, its application, benefits, operating window and limitations are not deeply managed by the oil & gas industry community.

The compressor boosts gas flow rates by increasing the pressure drawdown in the well proportionally to inlet pressure reduction. The required pressure ratio needs to meet the discharge pressure requirements to overcome well head pressure, column weight and pressure losses across the tubing, but the larger pressure ratio is the higher outlet temperature will be, which may become a limiting factor due to completion, compressor and process specs. Fluid velocity also varies across different casing sections, carrying with changes in liquid volume fraction (LVF) and flow regimes. In general, compressors are known to be low efficient handling liquids, therefore a close investigation on the LVF and flow patterns at inlet conditions must be very well understood for downhole applications.

Well modeling and sensitivity analysis will be used in this paper to illustrate in detail the well performance representation with downhole gas application along with a comparative analysis with surface gas compression to evaluate potential gains. Results and observations about these parameters, along with methodologies to calculate inlet/outlet conditions will also be described in this paper, adding to the existing literature a new holistic approach for analyzing gas well performance operated with downhole compressors.
Measurements of the Inorganic Scale Buildup Rate on Downhole Completion Equipment – Debris Barrier Screens
Authors: Morrow Timothy , Al-Daghar Tariq , Troshko Andrey , Schell Caroline , Keller Michael , Shirazi Siamack , Roberts Kenneth
Published: November 2018

The long-term development plan for a giant oil field offshore Abu Dhabi calls for new extended reach wells drilled from artificial islands. The existing wells in this field have historically suffered from inorganic sulfate-based scale deposition in the production tubing which is mitigated by periodic scale inhibition squeeze treatments. The new extended reach wells will have more sophisticated lower completions, including limited-entry liners (LELs) and inflow control devices (ICDs) with external debris barriers. It is currently planned to mitigate inorganic scale in these wells with periodic coiled tubing or bullhead scale inhibition squeeze treatments, which are anticipated to be more challenging and costly due to the extended reach. It is unknown as to whether these types of completion equipment are susceptible to scale deposition or how much scale deposition can be tolerated before well productivity is impacted.

Knowledge of the rate of scale buildup on ICDs and LELs versus the volume of water produced through the devices is an important factor for choosing the optimum frequency for scale inhibition squeeze treatments to mitigate scale in these completions while keeping operational costs down. A two-phase laboratory study is currently underway to assess the susceptibility of ICDs to scale deposition. The first phase of the study will focus on the potential for strontium sulfate scale deposition on the debris barrier upstream of the ICD.

This paper reports the experimental design and results of laboratory scale deposition experiments on a series of debris barrier test coupons with the goal of estimating the rate of scale buildup on the full-size ICD debris barriers, and the volume of scaling brine that can be produced through the ICD debris barrier (in the absence of any scale inhibitor chemical) without risking significant plugging.
Simulation and Testing of an Isolator Tool for High-Frequency Torsional Oscillation
Authors: Heinisch Dennis , Kulke Vincent , Peters Volker , Hohl Andreas , Schepelmann Cord , Reckmann Hanno , Ostermeyer Georg-Peter
Published: November 2018

During downhole drilling, severe vibration loads can occur that affect the reliability and durability of tools in bottom-hole assemblies (BHA). These high-frequency torsional oscillations (HFTO) can cause premature damage to tools or their subcomponents. This paper presents dynamic simulations, prototype testing, and field test results of a BHA component that isolates the upper part of the BHA from HFTO. This isolation increases the performance and reliability of BHA components through reduction of the vibration load.

The paper provides a brief summary of the theoretical background for predicting the critical torsional eigenfrequencies, mode shapes, and susceptibility of BHA design to HFTO. Finite-element (FE) models were used to simulate the effect and efficiency of the isolation. The isolator tool was tested in a full-scale laboratory test setup that emulated the critical mode shapes to analyze the torsional dynamics and the expected isolation effect. A BHA with the isolator tool positioned between a rotary steerable system (RSS) and measurement while drilling (MWD) tools was excited in the critical HFTO mode shapes with an electrodynamic shaker. Vibration response was measured using triaxial accelerometers.

Later, the tool was tested in the field in a BHA configured to log the vibration below and above the tool at sufficiently high sample rates to validate the isolation effect of the tool.

The laboratory results showed the isolating effect between BHA components above and below the isolator tool, in particular for the critical HFTO-frequencies and mode shapes as predicted by the finite-element simulation. The torsional deflection shapes from testing using distributed triaxial accelerometers showed a high correlation with the predicted mode shapes from the FE model.

The measurements from the field test also identified the isolation effect between the BHA sections. The measurement data showed that as predicted only the lower part of the BHA below the isolator tool oscillated at non-critical torsional eigenfrequency.

The isolator tool reduced torsional vibrations and improved tool reliability, tool lifetime and service delivery, especially while drilling in formations that are susceptible to excite HFTO.
A Case Study on Open-Hole Logging While Tripping LWT Through Drill Pipes, as a New Technology for Risk Mitigation and Cost Optimization in Abu Dhabi Onshore Fields
Authors: Singh Maniesh , Al Benali Khaleefa , Sallam Yassin , Sajeel Kashif , ElWazeer Fathy , A. Chaker Hicham , Propper Maarten
Published: November 2018

The ability to measure formation petro physical properties thru drillpipe has always been a challenge. It requires unconventional approaches to remove the effects of metal and borehole fluids on both the transmitted and received logging signals. This paper will present a proven technology executed in more than 1,000 wells all over the world and a first two successful trail case study from ADNOC Onshore wells in the Middle East.

The main objective is to acquire triple combo data (resistivity, density, neutron, gamma ray, spectral gamma ray & caliper) using the LWT conveyance and acquisition technology where there is a high risk of downhole triple combo Logging While Drilling (LWD) and or wireline (WL) tools getting stuck and the risk of losing radioactive sources.

The new patent pending technique was executed by using a slim downhole measurement tools inside specially designed drill collars invisible to the measurement sensors. LWT collars can be used for drilling and reaming as with normal drill collars. Propagation resistivity and neutron measurements are mostly like conventional techniques in tools physics. Density and nuclear caliper are measured by modelling the responses of three detectors short, medium and long distance away from the cesium source.

The measured LWT log data has been validated through back to back comparisons with WL & LWD) logs showing almost one to one correlation considering the effects of mud invasion due to lapsed time between runs, different wellbore condition and different depth of investigations.

Measured caliper, resistivity, density, neutron from LWT showed respectable match with WL or LWD tool. The differences in log responses are explained by differences in tool physics, logging speeds and environmental conditions. Similarly, the computed porosity from LWT tool comparison with WL and LWT porosity has almost the same statistics. The Quality LWT data was acquired in both wells at virtually zero LIH risk and minimum extra drilling rig time.

Introducing the new LWT technique to measure accurate Open Hole formation evaluation data from inside the drill-string is a cost-effective solution in various challenging scenarios, Exploratory/ Appraisal/ Development risky & challenging wells with unknown reservoir pressures or unsystematic depletion scenarios, complex downhole in-situ stress regimes, challenging tectonically faulted or fractured areas & unstable shales and many more, posing challenge to drill stable holes and a threat to LWD/ WL radioactive tool stuck.Unplanned deviated 8-1/2’ hole section geo-steered by MWD-GR, where at last minute triple combo is desired.
Impact of Natural Fractures in Reservoir Modelling and Characterization. Case Study in UAE
Authors: Mandl Johannes , Mills Carey , Obaidli Eissa Al , Basioni Mahmoud , Ali Khalfan Al , Blooshi Ahmed Al , Belova Natela , Arroyo Elkin
Published: November 2018

The offshore Field-A Gas Development Project is an integral part of the Abu Dhabi Deep Gas Project targeting untapped hydrocarbon reserves with priority given to gas reservoirs to satisfy an increasing gas demand and sustain economic growth of Abu Dhabi Emirate.

Well test data from Field-A Khuff Formation cannot be modeled solely using a matrix based porosity system and requires the presence of fracture network to give a "mixed" porosity system to explain the observed flow test results. To assess this a subsurface study was initiated to incorporate fractures within the matrix porosity based 3D reservoir model and to examine different methods of populating fracture distributions across the geologic model. The ultimate aim of this work was to more accurately predict gas rates to better understand and mitigate rate uncertainties across a range of development scenarios.
Ultrasound Tomography Based Two-Phase Composition Measurement
Authors: Ahmad Talha J. , Li Weichang , Adams Robert , Deffenbaugh Max , Arsalan Muhammad
Published: November 2018

Reliable flow measurement at the surface is critical for production optimization and reservoir management. Commercial water-cut and three phase flow meters have limitations in accuracy over the range of multiphase flow conditions. They require frequent calibration, and have high capital and operational cost. This paper describes an ultrasonic tomography based measurement of water hold-up, and presents preliminary flow loop and field test results. This ultrasonic system has the potential to overcome certain limitations of existing metering solutions.
Advanced Spectral Modeling of Noise Log Data: The Key for a Comprehensive Downhole Dynamic Characterization
Authors: Rocco François , Pirrone Marco , Galli Giuseppe , Moriggi Sara
Published: November 2018

This paper discusses the enhanced use of noise logging aimed at characterizing the dynamics of complex reservoirs and addressing wellbore integrity issues. The methodology makes use of a fit-for-purpose quantitative spectral analysis of noise log measurements and can provide direct and fast information about well completion integrity, post-stimulation job efficiency, fluid flow path in the near wellbore region, reservoir porosity characteristics and flow-units identification.

The approach is presented by means of a study performed on several wells intercepting different heterogeneous reservoirs and characterized by complex completions and, sometimes, by intensive stimulation jobs. In details, a high-resolution noise pattern modeling in a wide frequency range is performed to discriminate the character of the recorded flow noise in terms of mesopores, macropores, fractures, behind-casing channels and completion elements (including active valves and leaking packers). In favorable scenarios, the noise power amplitude is also used to understand the contribution of active reservoir units.

It is proven that providing a quantitative noise pattern classification is fundamental to recognize unusual poor cement placement issues, not detectable by standard sonic and ultrasonic cement logs and to discriminate between leaking and sealing packers. Moreover, in case of acid and/or acid fracturing treatments in carbonate reservoirs, the methodology can identify the generated wormholes/fractures and quantitatively evaluate the efficiency of the stimulation jobs by means of noise power analysis in the related frequency range. In addition, a dedicated spectral noise modeling is also used in order to identify flow-unit contributions in multi-layer scenarios and the type of porosity providing the flow. The reliability of the workflow comes after a successful comparison with the available standard production logging interpretations. The integration of this approach with standard workflows completes the reservoir characterization providing additional dynamic outcomes.

The key role played by the enhanced modeling of spectral noise log data demonstrates the versatility of the methodology. Although the added values of this logging technique are already known, the quantitative use of noise power amplitude in selected frequency ranges is relatively new and can shed light on this topic for future advanced applications.
Tipping the Scale in LNG Plant Design: Considerations for Train Size, Driver Selection, and Adopting Digitalization
Authors: Guccione Danielle , Russell Matthew
Published: November 2018

In recent years, there has been a great deal of discussion surrounding the topic of mid-scale vs. large-scale liquefaction trains in LNG export facilities. While in some select cases, mid-scale trains (0.5 – 2 million tonnes per year (typ)) may offer commercial, executional, and financial advantages, the decision is not a simple matter of one-size-fits-all, as large trains (>3 million tpy) offer economies of scale, among other benefits. As this paper will explain, choosing a solution that delivers the most value over the life of a facility is contingent on the operator's specific objectives and circumstances. Ultimately, train size and liquefaction licensor selection have only a marginal impact on project capital costs as long as the total facility achieves a minimum of 8 million tpy (Russell, 2018).

The paper will offer objective cases for building both mid- and large-scale trains and outline key areas for project stakeholders to consider when making an informed decision regarding capacity and liquefaction licensor. It will also discuss important considerations for optimizing LNG plant design, such as mechanical driver selection, modularization, and the incorporation of digital technologies. The paper will conclude by discussing the importance of adopting a holistic strategy that integrates the entire gas value chain when attempting to drive out costs, minimize risk, and maximize overall project economics.