bluuebunny/crossref_metadata_2025 huggingface dataset:
LNG Flexible Integrated with Fiber Optic Distributed Leak System Enhancing Safety, Integrity Monitoring and Life Assessments
Authors: Abbasi T , Hults J. E. , Mesnage O , Simoes V. , Gerez J. , Hardiman R. , Vlekken J. , Roosbroeck J.
Published: March 2016

Objectives/Scope

Leak Detection (LD) in critical pipelines and fluid transfer systems is a key requirement for the future of the petroleum industry in terms of assuring the health and safety of personnel, the public, the environment, and assets. For the LNG industry, safe transfer of LNG between production facilities (e.g. FLNG), tankers, and storage systems is essential. Assurance of integrity and safety should be pursued continuously in these systems, and effective LD systems can act as an early warning, allowing for safe mitigation of risk.

Methods, Procedures, Process

Current pipeline LD systems typically use Computational Pipeline Monitoring techniques. However, these LD systems have limitations in terms of their achievable minimum leak detection threshold and detection timing issues requiring a different approach be developed.

One such approach that is attracting much attention is the utilization of Fiber Optic (FO) systems. These may provide lower leak detection thresholds, shorter detection time coupled with extended range detection monitoring of long, e.g. 400+ m flexibles. FO Digital Temperature Sensors (DTS) have already been used for temperature measurements on flexible pipes and pipelines over several kilometers long. In Situ LD systems may possibly allow earlier detection of small leaks that are outside the capability of currently available systems. Being able to detect leaks with a real time LD may be very advantageous. This paper presents recent developments in design, integration, and testing of FO systems, which can provide detection of leaks in offshore pipelines and flexibles.

The use of FO sensing for offshore pipeline leak detection is still in its infancy and is emerging for cryogenic flexibles. New LD technologies are being developed for improving not only sensitivity, but, also how to reliably and economically deploy the system in situ in a LNG Flexible.

Results, Observations, Conclusions

Several FO sensing technologies, including Raman, Brillouin and Fiber Bragg Grating (FBG) are under evaluation for Technip LNG flexibles. A quantitative/qualitative comparison of available FO solutions including deployment considerations in a flexible are discussed and presented in this paper.

Novel/Additive Information

What else can be done with this system? Other potential uses are to monitor stress or strain along the entire length of the pipe, provide a continuous temperature measurement, flexibles shape, etc. This type of monitoring may be coupled with Computational Fluid Dynamic (CFD) models to improve integrity and safety predictions.
Review of Bonded Rubber Flexible Hose Design Codes and Guidelines in Relation to Sea Water Intake Risers on FPSO Vessels
Authors: Craig Ian
Published: March 2016

Sea Water Intake Risers (SWIR) used on Floating Production Storage and Offloading (FPSO) vessels generally comprise of a series of bonded flexible rubber hose sections suspended as a free hanging cantilever from the underside of the vessel, a configuration unique to this application. This paper identifies the industry codes and guidelines associated with the design and manufacture of bonded flexible rubber hoses and determines those most appropriate for a SWIR application to assure the satisfactory operation and life in field.

The associated industry codes and guidelines are analysed and critically appraised to determine which provide the most relevant verification and validation criteria for the design and manufacture of bonded flexible rubber hoses used in a SWIR application with due consideration given to the specific requirements of these bonded flexible rubber hoses which, in addition to the transportation of untreated seawater, also need to accommodate the loads induced by self-weight, vessel motion and environmental forces.

The paper concludes that there are a number of industry codes and guidelines related to the design and manufacture of bonded flexible rubber hoses. However, whilst there are criteria from several of these industry codes and guidelines that may be applied, the design and manufacture of bonded flexible rubber hoses for a SWIR application is not specifically covered by the scope of any one of the documents reviewed. Consequently, the paper identifies the most relevant criteria from the reviewed documents and sets out a propped methodology to verify and validate the design and manufacture of a flexible hose in a SWIR application.

Although this paper proposes a set of verification and validation criteria specifically intended for the design and manufacture of bonded flexible rubber hoses used for SWIR applications on FPSO vessels, it should be noted that these systems are also currently being considered by several stakeholders for similar application on the emerging Floating Liquefied Natural Gas (FLNG) vessels.
Tension Leg Platform Design with Consideration of Tendon Springing and Ringing
Authors: Teng Y. , Tan J. H. , Kim J. , Jang H. , Baquet A.
Published: March 2016

This study presents two tension leg platform (TLP) conceptual designs to account for different environmental conditions including water depths in the Asia Pacific region. The TLPs are designed for similar functional requirements to support relatively small topsides for dry tree systems. Hull global motions are calculated using proprietary and commercially available simulation tools. For one of the two TLPs, tendon springing and ringing responses are calculated using advanced numerical methods, i.e. Computational Fluid Dynamics (CFD) with additional user codes based on Euler Overlay Method (EOM) and a newly developed fully coupled hull and mooring analysis procedure.

This study shows that TLPs can be designed for different environmental conditions and they can potentially be scaled down to cater for smaller wellbays or to use tender assisted drilling (TAD) on the platform. The CFD methodology presented for tendon springing and ringing analyses can be used to complement model-scale laboratory testing which has been the only means to obtain these high frequency responses, until the present time.
Perched-Water, the Concept and its Effects on Exploration and Field Development Plans in Sandstone and Carbonate Reservoirs
Authors: Gaafar Gamal R , Altunbay Michael M. , Aziz Shaharudin B A
Published: March 2016

Perched-water conditions have been observed infrequently in oil and gas fields in zones above fine-grained material that may be located a few to 100 meters above the oil water contacts. Although infrequent in scale of number of fields globally, perched-water zones are important consideration when evaluating reserves and planning field development. The study described in this paper was conducted to examine perched-water conditions and quantitatively evaluate factors that control perching behavior and its impact on field development plans.

The differences between perched-water and hydrodynamically-tilted contacts have to be understood and clearly identified in a given reservoir by studying geological controls. The geological controls that shape contacts either perched or hydrodynamically tilted do play vital role in field development plans because of their structural differences leading to pressure communication or the lack of it. A perched-water zone in subsurface is defined as a water-saturated zone that is above contact or as a water-saturated zone not-directly-connected to the regional oil-water contact. Perching phenomena may occur in a permeable layer overlaying a relatively impermeable layer and conditions that could force water to infiltrate vertically through low permeability layer.

The stress conditions that lead to formation of perched-water are extraneous. However, petrophysical properties of the subject rock that is exposed to the prevalent conditions determine the viability of formation of a perched-water structure. Hence, neither structural geology, stratigraphy and depositional environment studies nor facies and petrophysical evaluations can be performed alone to decipher if a structure is/can be considered "perched-water". Therefore, the cases evaluated in this study are interrogated from structural, hydrodynamic and petrophysical perspectives to decide if subject structures can be deemed to contain "perched-water". The correct diagnostic brings additional hydrocarbon pore volumes or cost savings when drilling below apparent hydrocarbon-water contacts with misconception of a probable perched-water both affecting the financial positively
First Remedial Sand Control Treatment Case Study from Sumandak Field in Malaysia
Authors: Samvelova Marina , Priatna Oktaf , Kristanto Tutus , Thian Kelvin , Rosland Eadie Azahar B , Sandanasamy Ronfernandez , Tashkenbaev Timur , Kwang Hui Nicholas Foo , Rechoum Hassan , Fraser Mark
Published: March 2016

The Sumandak field is located offshore Sabah, northwest of Labuan Island, in Malaysia. The majority of the reservoirs in this field are oil producers subject to sand production at some point during well life.

The subject well was completed using a typical completion design for the current field, running standalone screens inside an 8.5-in. open hole using 3.5-in. dual and monobore production tubing strings. Several wells in the study field are shut in and not producing because of the significant amount of sand and fines produced to surface facilities and filling the tubing, thus negatively affecting production. To reactivate the wells, remedial sand control techniques were necessary to restore productivity of the reservoir.

This paper presents a through-tubing recompletion method combining mechanical techniques, such as a through-tubing intervention approach, along with downhole equipment and a chemical approach that used a fines control treatment, which helped bond the formation fines in place to assist with restoring initial cementation of the reservoir and reduced the risk of blocking the screen media.

The success of this operation was aided by an intensive laboratory study of cores from the field to optimize the design of the tool assembly and treatment formulation based on the particle size distribution (PSD) profile and production histories from the described wells.

Through-tubing downhole tools were chosen considering tubing and casing sizes, the wellbore minimum restriction, type and locations of the landing nipples, reservoir properties, bottomhole pressures, packer setting depth, length of the reservoir to be recompleted, location of the interval in relation to production tubing, length of the rat hole below the interval, and consideration to repair an existing but possibly damaged standalone screen. An advanced wellbore-cleanout technique for low bottomhole pressure reservoirs that uses an upper jet and washdown jet nozzles in conjunction with coiled tubing (CT) was performed before the consolidation treatment.

This is the first time a through tubing recompletion of the existing wellbores has been implemented in the Sumandak field in offshore Malaysia. This methodology has integrated new and existing technologies to achieve successful sand control operations to bring a well back on production after having been shut in because of sand production. It helped reactivate the wells and improve the recovery reserve rate of the field.

After this successful treatment, productivity of the well has exceeded expectations compared to conventional gravel packed wells. Such placement techniques created many opportunities to effectively and economically treat and revive wells experiencing similar production issues.
A Streamlined Product Development Process for Permanent Downhole Gauge: Key to High Operational Reliability in HPHT Wells
Authors: Balasubramanian Aswin , Flygare James , Shrivastava Pankaj , Smith Callum , Buchan Martin , Quaden Roy
Published: March 2016

A permanent downhole gauge (PDG) in an intelligent completion provides real-time data concerning downhole conditions that can be used to assess the well environment and make informed decisions regarding reservoir and well integrity management. These gauges are permanently installed in severe downhole environments and rarely retrieved to surface for analysis or maintenance. Despite harsh conditions, the gauge is designed to achieve high operational reliability at temperatures of up to 200°C and pressures that reach 30,000 psi. The scope of this paper includes successful application of design for reliability (DfR) principles to streamline the product development process for high-pressure/high-temperature (HP/HT) environments.

Equipment and material reliability is critical to success in HP/HT environments. This paper discusses a reliability focused product development approach and highlights the application of DfR techniques used to qualify a downhole gauge for an operator's prelude floating liquefied natural gas (FLNG) project offshore northwestern Australia. In this major well development project, downhole gauges are used for real-time permanent monitoring at high temperature downhole conditions.

High operational reliability of a downhole gauge is important to ensure functionality throughout facility commissioning, startup, and operations after a well suspension period. Reliable recording of well integrity data during the well suspension period also helps improve operational simplicity.

The DfR process is a systematic, streamlined, and concurrent engineering program designed to meet system reliability targets. This paper examines establishing a reliability specification for a downhole gauge, managing design risk using design failure mode and effect analysis (FMEA) followed by design robustness testing using highly accelerated life tests, leading to a reliability demonstration test program to achieve target system reliability.

This paper highlights an application of optimized DfR strategy along with an efficient reliability qualification test that resulted in successful product development. Improvements to the quality process to ensure reliability consistency between testing and the final commercial deployed gauges are also addressed in this paper.

Additionally, this paper highlights strategic application of a powerful DfR process that aided design de-risking and helped attain system reliability targets, thereby, helping the operator meet its needs. Also demonstrated is how an efficient DfR process led to streamlined product development of a permanently installed downhole gauge resulting in cost and time-to-market improvements while establishing reliability.
Aquatic Oil Spill Remediation by Using Automated Unmanned Boat AUB
Authors: Imtiaz M. , Rajak V. K. , Dei S. , Chhateja J. , Biswas A.
Published: March 2016

The paper briefly discusses the present trend in removal of slick, and puts forward a revolutionary methodology for the same in the form of CSASSB, Cok Sorbent carrying Automated Sub-Surface Boats.

The paper is divided into two parts, the first part discusses the effectiveness of the use of CSASSB's and compare it with the currently used counterparts. The second part discusses the suitability of cork as the appropriate absorbing material. The cork absorbent material is subject to a heat treatment to uncrease its hydrophobicity, its lightness and absorbtion capacity. The working of CSASSB's involves a five step process. The above paper discusses all the above mention steps in detail.

The CSASSB is considerably more fuel effective and eco-friendly than the current ships that are used for the remediation of aquatic oil spills. This system is simple, yet effective. Moreover, the heat treated cork as a sorbent for oil removal in aquatic environment with advantage of being a natural and ecological product. Hence, the CSASSB system with the aid of cork sorbent keeps the ecosystem healthy by removing toxic slick.

The utilization of automated unmanned boats for the skimming of oil has not been introduced. This paper underscores on the feasibility and the advantages of deploying an autonomous vehicle for the same.
Consistent Design Criteria for South China Sea With a Large-Scale Extreme Value Model
Authors: Raghupathi L. , Randell D. , Jonathan P. , Ewans K. C.
Published: March 2016

Existing metocean design criteria for offshore facilities in the South China Sea have been estimated using different data and procedures, some of which are at least partly ad hoc. As a result, it is probable that existing criteria are inconsistent, in the sense that assets designed to the same design codes have different realised levels of integrity. To address this concern in this paper, we apply a large-scale extreme value model adapted to parallel computing environment, applied to the recent high-resolution SEAFINE hindcast database. This not only ensures design criteria that are statistically and spatially consistent but is also faster by avoiding the need for repetitive site-specific analysis.

We have to overcome several challenges before we can apply a large-scale extreme model on the SEAFINE database. These include identifying a spatially consistent set of storm peaks and validating the hindcast data with real measurements. We then estimate marginal return values for significant wave height for locations within a large spatial neighbourhood, accounting for spatial and storm directional variability of peaks over threshold. A quantile regression identifies the extreme value threshold, the rate of exceedance of which is described using a Poisson process. The size of threshold exceedances is described by a generalised Pareto model. The characteristics of the threshold, rate and size models are all non-stationary with respect to directional and spatial covariates, parameterised in terms of (multi-dimensional) penalised B-splines. Parameter estimation is computationally challenging, but a combination of efficient generalised linear array algorithms executed within a parallel computing environment enable maximum likelihood estimation of all models. Bootstrap resampling is used to estimate uncertainties of model parameters and return values.

We thus estimate consistent marginal return values for significant wave height and their uncertainties, at all locations in the spatial neighbourhood. In addition, we quantify directional variability of return values across different return periods. We rigorously validate the proposed spatio-directional model with that of a direction-only model by deriving model diagnostics for the same site and demonstrating equivalent goodness of fits. To our knowledge this is the first of a kind of application of large-scale estimation for the South China Sea. With this approach, design criteria for large spatial domains, non-stationary with respect to the appropriate environmental covariates, can be estimated efficiently, consistently and with quantified uncertainty.
Case Study - Engineered Fiber-Based Loss Circulation Control Pills EFLCC Solves Total Loss Circulation Challenges on Complex Depleted and Fractured Formation in Natuna Sea, Indonesia
Authors: Jaffery Maimoon , Wicaksono Adithya , Pasteris Mathieu , Subhan Muhammad , Amir Baso , Mansur Mohammad
Published: March 2016

The loss of circulation during well drilling and cementing jobs is a serious problem for the oil and gas Industry. Loss of time is very costly and wellbore erosion can lead to inadequate zonal isolation putting the long-term integrity of the well in jeopardy.

Lost circulation was a major challenge experienced by an operator when drilling wells in their 2011 campaign. The site geological prognosis indicated a high degree of depletion in sands and presence of natural fractures. As anticipated, severe lost circulation while drilling was experienced in these formations and drilling efficiently proved to be a challenging process due to heavy mud losses.

An engineered fiber-based loss circulation control pills (EFLCC), based on special engineered fiber system and using a particle size distribution principle were developed to address this issue. The combination of fibers, special solids, and cementitious material was designed and tested in the laboratory to validate its ability to bridge the loss zone while permanently sealing the losses allowing further drilling to the next casing point.

This paper presents the case history and field application of these novel engineered fiber-based loss circulation control pills for the successful treatment of heavy mud losses to formation in wells in offshore gas fields in Indonesia. The paper also includes a discussion of the methodology, material properties and applications.
Well Completion Design Integrity Evaluation Including Thermal and Stress Analysis for Complex Well Completions Offshore
Authors: Chakraborty A. , Asba Madzidah A. B. , Shahreyar N. , Finley D.
Published: March 2016

This paper provides an overview of an engineering design methodology which uses a tubular design analysis validation software program that provides an analytical method for assessing tubing loads, design integrity, and buckling behavior under complex mechanical, fluid-pressure, and thermal-loading conditions. The design methodology is applied to complex wells (e.g., multizone, multistring completions, and intelligent completions). Tubing load evaluation cases for different operating phases are presented for two complex completion types viz. Intelligent Completion and Mutlizone Dual Completion.

Two (2) well study models are presented for discussion and evaluation of thermal and stress-loading analysis: the first model analyses a dual string completion, and the second model analyses an intelligent well completion. Thermal simulation is first performed followed by tubular stress modeling for tubular selection and design. Well models are focused to present tubing-design integrity analysis for multistring and intelligent completions with various anticipated operating loads during the life of the well. Analysis includes scenarios for simultaneous production/injection, commingled zonal flow control with multiposition interval control valves (ICV), and various other well-operating conditions.

Results show temperature/pressure changes for each simulated load scenario in the modeled wells. Also discussed are the impacts of well-operating temperature and pressure change on tubular axial loading, burst and collapse limitations, pipe movement and buckling potential, and resultant forces on completion packers in a multistring (dual completion) caused by tubular stress loading. Furthermore, tubular thermal and stress analysis is discussed for a multizone commingling intelligent well completion having multiposition ICVs with varying flow/injection rates. Results of thermal and stress modeling are evaluated to select and optimize the well completion design as well as identify well operating limits with respect to a set of combined ICV opening positions during commingled well operations.

Dynamic and complex offshore conditions can cause variations in operating temperatures and pressures in multistring and intelligent well completions in which design margins are slim because of production-casing diameter limitations. A detailed stress-loading analysis aided by thermal- and stress-analysis software provides methods for balancing completion design vs. risk. This process provides savings by optimizing well design to meet design integrity standards without being overdesigned.
Optimization of Injection and Production Parameters for Sour Gas Storages: A Case Study
Authors: Chen Z. , Liao X. , Zhao X. , Chen C. , Zhu L. , Zhang F. , Mu L. , Zhou X.
Published: March 2016

To meet with the energy strategy, some natural gas reservoirs in Ordos Basin are planned to use as gas storages. However, most of the gas reservoirs have high content of H2S. If they were operated without parameters optimization, it would put reservoir engineers as well as the environment at rick. Thus, optimization of injection and production parameters of these sour gas storages is urgently needed.

In the paper, using numerical method, the movement mechanism of H2S is studied. With the sensitivity analysis, the effects of some critical factors on H2S mole fraction in produced gas are investigated including ultimate recovery factor, injection rate, production rate, and injection-production rate ratio. Based on the results of the sensitivity analysis, optimal injection-production parameters are selected for a gas storage S24 in Ordos Basin.

The results show that the H2S mole fraction in produced gas decreases as the injection-production cycle number increases. When the cycle number reaches 5, the H2S mole fraction is relatively stable. Additionally, the H2S mole fraction in produced gas hinges heavily on ultimate recovery factor, injection rate, production rate, and the injection-production rate ratio. The decrease amplitude of H2S mole fraction increases as ultimate recovery factor, injection rate, and injection-production rate ratio increase; it decreases as the production rate increases. Numerical results show that after 4 cycles of the operation with the optimal parameters, the produced natural gas from S24 gas storage can reach the quality standard II of commercial natural gas, which is safe for humans and environment.

This study provides us with key technical references for operation of the sour gas storages to ease the contradiction between energy supply and demand.
Realising Un-Swept Potential in Channelised Reservoirs of a Brown Field Using Well Placement Technology
Authors: Mohd Razak S. , Aldha T. , Ismail M. N. , Santoso G. I. , Alang K. A.
Published: March 2016

Rapid production decline of a mature brown field with high density of oil wells has triggered the need to search for trapped and undrained oil to arrest the decline. The field, ABC is located within the Malay Basin offshore Peninsular Malaysia and has been producing since 2002 with 40% reserves already drained. Recent reservoir studies have shown that oil pockets trapped in structural highs in water flooded reservoir and in structural lows in reservoirs with thick gas cap are unable to be drained with existing wells. Horizontal wells, with the aid of well placement technology were drilled to realise the potentials and increase field production.

An integrated approach utilising data from reservoir static and dynamic models and seismic interpretation were used to identify targets in areas of structural highs and lows. Economically viable prospects were selected based on remaining reserves, sand thickness, structure, fluid contacts and locations of nearby water injectors/producers and confirmed by a pilot hole. Based on the results, horizontal well placement is designed with the aid of an imaging tool using resistivity inversion to identify the base or roof of sand to ensure optimum standoff from fluid contacts to prevent early water encroachment or premature gas coning.

Two (2) horizontal wells were drilled with this approach. The first well, X targets 7m of oil column in a structural high bounded by oilwater contact and downdipping top of sand. The pilot hole confirmed presence of oilbearing sand and well placement technology was deployed to geosteer the horizontal section. A 200m horizontal section was drilled 3m above oilwater contact resulting in production of 1500 bbl/day. The second well, Y targets 6m of oil column in a structural low bounded by gasoil contact and updipping base of sand. 70m of oilbearing horizontal section was drilled with 0.5m standoff from the base channel resulting in production of 1000 bbl/day. The usage of well placement technology has aided the subsurface team in landing the horizontal section by navigating the undulations at the base and top of the channel at a scale unresolved by seismic resolution. By analogue, the resistivity inversion confirmed the rugosity of base and top of channel sand in many similar clastic reservoirs. Due to the dynamic of producing reservoir and variability in reservoir quality, the observed fluid contacts are also different for different oil pockets in the same reservoir highlighting the risks that need to be considered when proposing future targets. This strategy coupled with the well placement technology has allowed the realisation of otherwise stranded few MMstb oil in this brown field. This strategy can be replicated for clastic reservoirs in mature brown fields around the globe facing a rapid decline in production.
AUV-Based Seabed Characterisation Using a Lightweight Towed Array System
Authors: Pallayil Venugopalan , Chotiros Nicholas P
Published: March 2016

Offshore technology operations often require knowledge about the properties of seabed and sub-seabed to aid in their drilling operations, identifying geo-hazards and building of sub-sea structures. The analysis of marine sediments from the core samples is also routinely carried out to detect any presence of near-surface hydrocarbon seepage, which is a strong indicator of presence of active petroleum system in the area under investigation. The most conventional and also much practiced way of doing this is by collecting seabed samples using corers. The core sample analysis provides valuable information with regard to the above requirements. However, the process of coring is complex and heavily resource intensive. As the core analysis can only provide localised information, to survey an area of interest many such core samples would have to be collected to have a clear understanding of the seabed properties. Acoustic technologies have been extensively used for remotely monitoring the seabed properties. A coring operation is often preceded by a seismic survey, which again involves huge resources. The explosive sound sources (air guns) often used with these systems have always been a target of criticism from marine mammal conservationists as it compromises on the safety of marine mammals. The advancement of AUV technology has opened up alternatives to remote monitoring of the seabed. Commercially available AUVs are operationally reliable and are often equipped with many acoustic sensors such as high-resolution side scan sonar and multi-beam sonar. As AUVs can operate pretty close to the seabed, it places less demand on the source levels of the sound sources reducing the risk for marine mammals. In this review paper we look at the feasibility of adding a towed array sensor to the AUV platform so that some of the benefits of conventional seismic surveys can be obtained at a relatively lower cost. Initial results from a shallow water indicate that the seabed type can be classified to a first level using this approach and comply well with the model predictions. The study also made use of the acoustic modem signals from the AUV as the signal source so that there was no need for a custom made source. Though this study was targeted more towards understanding the effect of seabed on the sonar performance, the technique can be adapted and extended for offshore applications.
Unconventional Drilling in Southern Sumatra Area. Evolving Technique for the New Drilling Culture
Authors: Dharma Dion Satria , Irawan Fikri , Hidayat Andri Mustari
Published: March 2016

Recent drilling operations in Southern Sumatra area, especially Jambi and South Sumatera district, have experienced various problems upon drilling the top section, intermediate section, as well as production section.

Overpressures, loss circulation and narrow window between pore and fracture gradient are common problems when drilling the top hole section. In some wells, coal caving and shale sloughing are claimed to be the reason of drilling day extension in this particular section. Overpressure zone within permeable system have cornered several field operators to activate well control system. Some field operators even had to experience blow out. The upper zone of intermediate section sometimes experience tight hole and shale sloughing, which require adequate drilling fluid management. In several wells, reactive shale is identified within the lower intermediate section, which requires the operators to utilize oil based mud to avoid clay swelling. Total loss circulation inflicted with high gas content is a normal condition when penetrating the intermediate and production section. This condition increases operational days when drilled conventionally with high potential of pipe stuck, complications in formation evaluation such as cuttings recovery and well logging, or even forcing the operators to side track the well due to sloughing. Extensive well bore clean out period also have been experienced by some operators when drilled with high barite concentration within the production zone.

This paper elaborates a new drilling convention that has been practiced by the operators within these areas, evolving the commonly known Managed Pressure Drilling technique into a culture when penetrating such problems. Success stories will be highlighted when drilling through the top section, intermediate, and production section presenting risks associated from economical and operational perspective.
HP/HT Carbonate Acidizing—Recent Discoveries and Contradictions in Wormhole Phenomenon
Authors: Karale Chaitanya , Beuterbaugh Aaron , Pinto Mario , Hipparge Gulam , Prakash Anand
Published: March 2016

Matrix acidizing is a technique used for stimulating carbonate formations. Fluids used for this purpose are routinely characterized in the laboratory by means of core flood testing. Though several key insights can be obtained using the laboratory core flood technique, simulating exact downhole environments and extrapolation of the results obtained to field-scale has proven challenging. This paper addresses two specific topics related to acid wormholing—upscaling laboratory results to field scenarios and the interaction of reaction products in high pressure reservoirs.

To study the upscaling of acid wormholing experiments in field scenarios, a radial core flood testing apparatus was set up to better mimic actual wellbore acidizing flow conditions. The effects of radial flow path and completion type (i.e. openhole versus cased hole) as well as the applicability of the upscaling wormhole propagation model were studied. Furthermore, CT scans of related core samples were performed to characterize wormhole patterns generated by acid dissolution. In addition, tests were performed at high pressures and flow rates to study the effects of the interaction of reaction products on the wormholing process at typical high bottomhole pressure values.

Results from radial core flood techniques showed significant differences in terms of pore volume to breakthrough (PVBT) based on well completion type. Further, a current upscaling algorithm for wormhole propagation modeling was verified by comparison to corresponding experimental data, thus demonstrating the suitability of described linear core flow testing methods for fluid characterization and data modeling. The wormhole propagation model (based on the use of fitting coefficient) is well-justified by the probability of increased fluid loss from the wormhole in the case of deeper radial penetration, which overall reduces the efficiency of wormholing. CT scan results revealed nonuniform radial distribution of wormhole propagation, thus shedding light on challenges associated with achieving 360° stimulation around the wellbore. Experiments at higher pressures showed that, at higher flow rates investigated (or beyond optimum) wormhole propagation has a higher than one third dependence on interstitial velocity, signifying that high pressure reservoirs require greater volumes of acid for proper stimulation. Experimental observations are presented to correlate the results obtained thus far and help resolve controversies between various publications.

Presented studies highlight the effects of higher pressure in acid wormholing and signify the need for proper volume accounting in terms of job design. A simple radial core flood technique has been developed in this work, and has an advantage in terms of diversion studies by providing a means of arranging high and low permeability core samples in the same order as formation layers and accounting for fluid entrance position.
An Efficient Geosteering Tool for CBM Drilling
Authors: Gao Wenkai , Sheng Limin , Chen Wenyi , Wang Lei , Zhang Liancheng , Peng Liexin
Published: March 2016

In CBM drilling, high-efficient, low-cost MWD and geosteering tools are needed to ensure the cost-efficiency of large-scale gas development. Especially in a cluster and horizontal coalbed methane well drilling environment, one of the most effective methods to enhance the individual well producing rate is to keep the bit always in the best position to extend along the target layer.

The DREMWD CBM drilling geosteering system adopts electromagnetic information transmission technology. Compared to traditional mud pulse technology, it has such advantages as a wide range of media applications, deep non-relay transmission, a fast signal transmission rate, and a low failure rate of field applications. Moreover, it can measure wellbore trajectory and geological parameters, so as to ensure actual wellbores to penetrate into coal seams and get the best position. Therefore, it has quickly become a leading geosteering tool for CBM drilling.

The DREMWD system consists of downhole tools and surface units. Downhole tools are mainly composed of the high-power generator, orientation sensor, natural gamma sensor, electromagnetic transmitter circuit, insulation transmitting antenna, and non-magnetic drill collar. Surface units are mainly composed of the signal receiver, ground antenna, driller display, and signal processing and analysis software. With its unique high-power downhole generation technology, greatly enhancing emission intensity and formation penetration. The rotary dynamic azimuth natural gamma measurement module is composed of a natural gamma sensor, a rolling angle sensor and a signal processing circuit. It can perform real-time measurement of the formation natural gamma within a certain fan-shaped range at upper and lower levels. The system has been widely used in the CBM drilling in Qinshui basin in China with good effect.

With this geosteering tool, the drilling performance and recovery efficiency have been remarkably improved. This paper will highlight the technical development and present helpful case histories and recommendations.
Seamless and Welded Tubes Alloy 825 for Sub Surface Safety Valve Control Line Application Evaluation
Authors: Soerowidjojo Kukuh Wanengkirtyo , He Wenle
Published: March 2016

Seam welded tube production technology has developed to a point where seam-welded tube quality reaches very closely to seamless tube combining advanced welding technology and drawing technique. Improvements have been gained over the years to minimize welding effects and smoothened both outer and inner diameter of the tube from welding material excess. Unfortunately, micro defects and metallurgical changes caused by welding are still present in the product that might influence its performance when it is used for sub surface safety valve control lines and also chemical injection lines.

High alloyed nickel based material UNS N08825 is selected in this study where similar dimensions and chemical composition were chosen in the observation by using electrochemical potentio-dynamic polarization in chloride solution, and scanning electron microscope (SEM), glow discharge optical emission spectrometry (GD-OES) for the surface analysis. The result of this investigation shows that the seam welded tubes have the same level of hardness with seamless tubes. Nevertheless, the weld defects along the fusion line could be the cause of diminishing corrosion resistance of the tube. Chromium nitride precipitates and lack of fusion have been observed in the outer tube surface of the Alloy 825 seam welded tubes which could not be detected by non-destructive testing (NDT) methods.

This study signifies that seamless tubing is a better option as SSSV control line to maintain well integrity than seam welded tube.
Behind Fault Well Planning: The Strong Influence of Geological Structure in Planning Complex Well Trajectories in the Gulf of Thailand
Authors: Kaeng Geovani Christopher , Natepracha Jatuphat , Sausan Sarah , Chongrueanglap Pongsit , Anansatitporn Natthanicha , Srisuriyon Kittipong
Published: March 2016

The Gulf of Thailand is characterized by pull-apart rift basins containing extensive en-echelon grabens and half-graben intra-basin fault systems. Both act as the pathway for hydrocarbon upward movement and as the trapping mechanism. The main reservoirs are compartmentalized sands and show rapid lateral stratigraphic changes because of their fluvial nature further segmented by faults. In this geological setting, the highest hydrocarbon pays often lie behind (upthrown side) the fault. To maximize the possibility of encountering trapped hydrocarbons, wells are drilled along and as close as possible to the fault plane. This paper reviews the impact of this complex geological setting on well trajectory characteristics and their planning aspects.

The Gulf of Thailand is also known for its fast drilling rate, which motivated operators to implement a factory drilling approach in their field development programs. The fast track nature of the drilling program requires an unconventional methodology to complete complex well plans in very limited time. The study revealed that strong collaboration between geoscientists and engineers are instrumental to significantly improve the well planning workflow. It further seeks to establish a preferred methodology through the implementation of integrated technology combined with a multidisciplinary collaborative culture. Using this methodology resulted in a significant improvement in terms of planning time and a better choice of trajectories.
Time-Lapse Seismic Feasibility Modelling and AVO Sensitivity Analysis for Quantification of Pressure-Saturation Effects in Fields Located in Malaysian Basins
Authors: Danaei Shahram , Hermana Maman , Rafek Abdul Ghani , Ghosh Deva
Published: March 2016

Time-lapse seismic has established itself as a valuable tool to monitor dynamic changes in oil and gas reservoirs. These changes occur continuously in a reservoir due to production and/or injection operations and are manifested broadly in pore pressure and also water saturation changes. These changes might occur either independently or concurrently and affect seismic wave velocities. Therefore, this can be studied by 3D seismic surveys from different times or 4D seismic. The change in seismic response can be large or subtle depending on the magnitude of dynamic reservoir changes. Time-lapse feasibility modeling is the practice that realizes whether a detectable 4D signal can be captured or not. In this research, a 4D seismic feasibility model has been developed to assess the possibility of obtaining a 4D signal in an oil zone located in the Malaysian basins. This model is based on different production and water injection scenarios and a new rock physics workflow. Gassmann fluid substitution has been used to model the effect of different water saturation changes on seismic velocities. For pore pressure changes, Hertz-Mindlin geo-mechanical model in conjunction with pore space stiffness theory and the constant ratio approach for sandstone is used to simulate the effect of various pressure changes on seismic responses. This 4D feasibility model is followed by amplitude versus offset (AVO) modeling to exam the sensitivity of AVO intercept and gradient attributes resulting from different injection and production scenarios. In 1999, the AVO analysis method was presented to estimate fluid saturation and pressure changes from time lapse seismic data. This research has tested the AVO method in an oil zone located in the Malaysian basins. Finally, it is shown that AVO intercept and gradient cross plot is capable of distinguishing between water saturation and pore pressure changes in this zone. Therefore, this can be generalized in the Malaysian basins, where the AVO method can be used to differentiate between pore pressure and water saturation changes from 4D seismic data.
Novel Technology to Achieve the Fastest and Cleanest Formation Sample Data: An Introduction to Focused Sampling Probe Methodology
Authors: Tomar Ashish , Parashar Sarvagya , Wu Ivan Zhia Ming
Published: March 2016

This paper presents a technology designed to obtain the most representative formation samples in minimum time with less contamination. An innovative formation testing technology using the new focused sampling probe and real-time downhole fluid identification service, which enables users to save time and expense by eliminating the need for long pump outs and a second run, particularly in deepwater wells with unconsolidated sand reservoir formations. Representative formation sampling requires minimal differential pressure to move fluid and is uniquely able to provide low-contamination samples in extremely difficult unconsolidated formations. The in-situ fluid ID sensor data, which included fluid density, capacitance, resistivity, pressure, and temperature information, was used in conjunction with contamination forecasting software to provide accurate fluid-contamination predictions.

The formation testing tool "focused sampling probe" delivers a purer fluid sample than the traditional sampling techniques with less pumping time. This decreases uncertainty in terms of establishing connectivity and flow assurance while increasing operational efficiency. The formation sampling service incorporates oval pad geometry with large surface area, resulting in lower forces acting on the formation sandface and reduced sanding. Fluid flow is segmented into an inner and outer flow section; fluids in the outer section will be more contaminated and will be discarded back to the borehole. Fluids in the inner section will be purer and very low contamination is achieved much faster compared to traditional pumpout. In some cases, contamination is too low to be measured. The large flow area of the oval focused pad results in higher flow rate than a circular probe. The fast and versatile pump in the formation sampling service enables reduced cleanup times.
Sand Control from a Supply Vessel: Mobile Fracturing Fleet Saves Rig Time in Subsea Completions
Authors: Agee Daniel M. , Sutherland Andy , Syifaai Arfi , Malik Badar Z. , Tsangueu Barbara , Emmanuel Ignatius , Peacock Kevin B.
Published: March 2016

This paper presents an overview of switching from rig-based sand control pumping equipment to a semipermanent vessel-based pumping setup. The design, installation, and implementation of a fracturing vessel for subsea sand control and stimulation will be covered in detail. The approach taken includes an analysis of benefits and drawbacks associated with rig-based and vessel-based pumping setups as well as the design and implementation of a vessel-based fracturing package. Additional topics discussed include determining specifications for appropriate vessel selection and best practices for vessel layout design to maximize the pumping fleet functionality while minimizing the health, safety, and environmental (HSE) exposure.

We analyzed a case study in which a fracturing fleet based on a platform supply vessel (PSV) was implemented in place of rig-based equipment. Use of the methodology described here eliminated 17.7 rig days, 1540 offshore lifts, 46 helicopter flights, and 55 supply vessel trips over 11 wells in a subsea campaign. Additionally, due to the enhanced mobility of the vessel-based equipment package, it was possible to service two rigs with a single fracturing fleet. The switch from rig-based to vessel-based equipment resulted in an average savings of USD 1.3 million per well including rig day rates, fracturing equipment rental, and other associated costs.