bluuebunny/crossref_metadata_2025_split huggingface dataset:
Subsurface Containment Assurance Program - Key Element Overview and Best Practice Examples
Authors: Schultz Richard A. , Summers Laine E. , Lynch Keith W. , Bouchard Andre J. 
Published: February 2015

The goal of Subsurface Containment Assurance (SCA) is to ensure that no adverse environmental impact, damage to operated assets, or impacts on well operations (drilling or production) occur due to leakage of production or injection fluids from reservoir intervals. Subsurface Containment Assurance involves the integrated efforts of subsurface (reservoir and overburden characterization), wells (planning, construction, well integrity and abandonment), operations (process safety and well operations and management of change) and HSE (health, safety and environment) teams. Disciplines must act together to develop and implement a surveillance plan to proactively monitor containment during well and injection operations in offshore fields.
The paper will describe the elements of a Subsurface Containment Assurance Program (SCAP) that are required for business units operating offshore across the entire life cycle from exploration to mature developments. The program is designed to be comprehensive, yet flexible; and focuses on the critical elements and risks for individual operating units. A consistent framework needs to be created and implemented that draws from existing tools for reservoir and overburden characterization and field management, and combines these tools to reduce the risk of unintended subsurface fluid containment loss. Specific assessment criteria and ranking approaches and tools for qualitative and quantitative estimation of containment risks will be discussed. Finally, surveillance programs focusing on containment using both direct and indirect measurements will be highlighted with a focus on offshore data gathering.
Loss of containment puts the environment, operating equipment and personnel at risk. Proactively identifying and mitigating containment risks is critical to operate safely. Containment assurance, particularly offshore, needs to be a key element of any asset and subsurface management plans.
The Tethered Catenary Riser Concept Application to Deepwater Fields in Asia
Authors: Legras Jean-Luc , Neel Nicolas 
Published: February 2015

Description
A new concept isproposed by Subsea7: the Tethered Catenary Riser (TCR). The concept consists ofa number of steel catenary risers supported by a subsurface buoy which istethered to the sea-bed by means of an empty single pipe tendon and anchored bya suction pile; flexible jumpers make the connection between the Floatingproduction Unit (FPU) and the buoy. The paper focuses on application of the TCRin deep-water fields of Asia.

Applications
Risers are de-coupledfrom the FPU. The riser system is thus efficient for FPUs with large motions: theflexible jumpers effectively absorb the platform motions, thereby the rigidrisers have very small dynamic motions, which improves both strength and fatigueperformance. The system can be installed before FPU arrival on site, whichimproves the time before first oil. The riser system is best designed for anumber of risers between 4 and 8 in addition to umbilicals, thus convenient forone or two drilling centres. The space used by a TCR on the field lay-out isrelatively small, thus allowing several units to be placed around the FPU inbetween mooring lines.

Results
The TCR system usesonly presently qualified material and technology. The components are all fieldproven as they are used in existing riser systems. Analyses have shown that, with adequate geometry of the buoy, the latter is sufficient stable to induceacceptable tilt when different arrangements of SCRs and flexible jumpers areinstalled, and under variation of the fluid weight distribution in risers. As a result ofinstallation studies, a method very similar to the one commonly used by subea7 for Single Hybrid Risers has been selected for the buoy and tether system. Placement of rigid risers, jumpers and umbilicals is as done by Subsea7 for theBSRs.

Significance
The TCR concept is a credible alternative option for use inincreasingly harsh environments or from host platforms with large motions. Asall components are fully qualified and the installation method well proven, theTCR system is cost effective and ready for project application.
The Effect of Appurtenances on the VIM Performance of a TLP for Southeast Asia
Authors: Tan J.H. , Teng Y. , Magee A.R. , Ly B.T. 
Published: February 2015

In Southeast Asia, the characteristic operating environment is strong and persistent currents with small to moderate waves, which encourages vortex induced motion (VIM) in floating platforms. Scaled model tests have been used by the industry to predict VIM in floating platforms. Numerical methods such as Computational Fluid Dynamics (CFD) analysis have the potential to complement model tests for predicting VIM. Hull appurtenances such as tendon porches, SCR porches, caissons, pipes, chains, fairleads and anodes interact with the boundary layer and affect the point of flow separation along the columns which controls the vortex shedding pattern of the hull. In this study, the effect of appurtenances on the VIM performance of a Tension Leg Platform (TLP) for Southeast Asian environment is investigated using a series of model tests and CFD analysis.
The findings from this study may be used as a reference to properly account for the effect of VIM. The measured/calculated amplitude of VIM may be used as input for additional load conditions to be considered in the design of the tendon mooring and riser systems.
Previous studies by others on the same subject were carried out for spars. Multi-column floating platforms do not have strakes on the columns unlike spars. Thus, significant difference in VIM behaviors between multi-column floating platforms and spars is expected. The wake is expected to remain turbulent in both full scale and model scale. For smooth cylinders, the separation point along the columns is scale-dependent and this may affect the VIM response. If the flow separates from a sharp appurtenance like a pipe, the VIM behaviors should be similar in full scale and in model scale. The results from CFD analysis generally agree with those from model test. The differences in the results from the two methods are discussed and areas for further investigation suggested.
Significant VIM can adversely impact the platform mooring and riser systems in terms of both strength and fatigue life requirement and has to be properly accounted for in the platform design. Left unchecked, VIM can lead to loss of production due to unplanned repairs of the risers.
Development and Application of Type Curves for Pressure Transient Analysis of Multiple Fractured Horizontal Wells in Shale Gas Reservoirs
Authors: Kim T.H. , Lee S.J. , Lee K.S. 
Published: February 2015

Horizontal drilling and hydraulic fracturing is necessary to reach economically success in shale gas reservoirs. PTA for shale gas reservoirs requires comprehensive understanding related to nonlinear gas flow process as well as hydraulic fracture properties. Even though significant progresses made in the past few years, there appears to be a lack of information regarding the characterization of shale gas formations. A major purpose of this study is to demonstrate how this issue may be addressed by pressure transient analysis for multiple fractured horizontal wells in shale gas reservoirs. Extensive numerical simulations were conducted to model transient pressure behavior of a fractured horizontal well and applied the results to well test analysis in shale gas reservoirs. The pressure transient response for a horizontal well with transverse multiple fractures is controlled by many of important fracture properties and nonlinear flow processes. This paper presents a comprehensive reservoir simulation model to investigate the characteristics of pressure transient responses under the influences of hydraulic fracture properties and nonlinear gas flow mechanism. Factors considered in this study include the number of hydraulic fractures, fracture half-length, fracture spacing, non-Darcy flow, and adsorption under reservoir flow condition as well as skin effect.
The numerical simulations for nonlinear gas flow provided various type curves in terms of dimensionless pseudopressure and time for transient pressure responses in fractured horizontal production wells. Results from type-curve matching for synthetic pressure data in shale gas reservoirs demonstrate that the conventional analysis approach may still be applicable for analysis of shale gas reservoirs. The results can be used for quantitative studies of transient gas flow behavior and determination of formation properties.
Successful Coil Tubing Based Selective Stimulation of a Remote Well in Challenging Offshore Environment - A Case Study
Authors: Anand Saurabh , Parasher Arunabh , Singh Alok Kumar , Kale Sagar , Gupta Karan 
Published: February 2015

Well XX-1 is a newly drilled producer well in offshore west coast of India. The well has a deviation of 65 Deg and is completed with 3–1/2" screens with 2.31" SSD's in 6" open hole. Post production line-up, the well PI was found to be very low (&lt;1). Thick viscous debris in the lower completion made access to the screen SSD's using slickline conveyed tools difficult and inconclusive - Hi Tech Downhole Camera runs confirmed that the lower completion was filled with mud. Tidal and current conditions ruled out any kind of Barge and Catenary based CT operation. Further, the platform had helideck as the working deck having a limited load handling capacity & crane load rating.
To remediate the poor well performance, a platform based coil tubing stimulation operation utilizing a modular and compact unit was proposed. A 20 T modular crane was installed on the platform and a detailed platform structural load analysis was carried out for spotting the CT unit and auxiliary equipment. Chemical & compositional analysis of the debris & formation cuttings was done to determine the appropriate stimulant recipe as no stimulation history for the field was available. CT conveyed Inflatable packer was used to isolate the lower section of the completion. Advanced flow activated downhole tools like double ended shifting tool & Impact hammers were utilized to selectively manipulate and stimulate all the desired zones in one run.
Post stimulation there was a 10 fold improvement in well PI with the well production increasing to 2600 BOPD from an initial rate of 300 BOPD.
The technique & setup has a huge cost implication as the cost of Catenary and barge is eliminated. The same technique is now planned to be applied to stimulate other wells in the field with logistical & technical constraints.
Well Test Analysis of Gas Condensate Reservoirs from Pressure Build Up and Draw Down Tests
Authors: Khosravi V. , Ketabi S. 
Published: February 2015

Condensate drops out around the wellbore in the gas condensate reservoirs when the well bottomhole pressure falls below the dew-point. In these reservoirs interchanges in fluid from single phase to multiphase in the near-wellbore region, causes three different mobility regions in the reservoir. At the outer region, Away from the well, pressure is still above the dew-point with initial liquid saturation and there is only gas existed (Region 3). Next, there is an intermediate region in which the pressure is below the dew-point with increasing in liquid saturation and the condensate drops out of the gas phase (regions 2). Finally, increasing in the liquid saturation reaches above critical value and both gas and condensate are mobile and flow together into the wellbore (region1).
This paper presents well test challenges on the gas condensate reservoirs. It demonstrates phase redistribution, double porosity, capillary number effects, partial penetration or composite behaviors. Many reservoirs in all around the world are affected by gas condensate behavior. For example, the Karachaganak field in Kazakhstan, the Cupiagua field in Colombia, the North Field in Qatar and the South Pars field in Iran. Consequently, many researches have been conducted since the 1950's to understand the behavior of the gas condensate reservoirs below the dew point pressure to determine the main controlling parameters.
To sum up, the draw down flow periods are extremely complex to interpret. Hence, it shows that the condensate banking effect can be removed completely with an excellent fracturing job in place, even though the well is depleted below the reservoir's dew point pressure. Along increasing the skin; it is important to note that the composite behavior is represented. Our studies have been performed mainly on build-up data, because draw down data depends on flow rate fluctuations due to noise; especially in the gas condensate wells. Before the final radial flow stabilization, Humping skin effect is observed and the dual porosity does not disappear immediately.
Global Ultimate Strength Assessment of Existing Offshore Jacket Structures
Authors: Ayob M.S. , Kajuputra A.E. , Mukherjee K. , Wong B.S. 
Published: February 2015

There are increasing numbers of ageing offshore structures in the water of South China Sea which come along with various types underwater structure anomaly, such as joint crack, member flooding, shallow gas and subsidence. This phenomenon brings an immediate attention to the Asset Owner to rectify the anomalies through various Strengthening, Modification and Repair (SMR) options. However, execution of SMR option is often a very costly operation. Optimum mitigation measure shall be established through proper structural re-assessment work with in-depth understanding of structural failure mechanism.
The present paper will focus on the established re-assessment methodologies in evaluating the structural global strength requirement. The re-assessment methodologies formed a step-wise evaluation process encompassing determining Risk Level Assessment, Design Level Assessment and Global Ultimate Strength Assessment (GUSA)
The risk level assessment considered all factors influences the likelihood of failure and consequence of failure of the structure to be determined to enable the establishment of its Risk Level. Next, the type of analysis which required to be performed under Design Level Assessment is similar to those analyses undertaken during Detailed Design Phase i.e. static in-place analysis, fatigue analysis, and dynamic analysis. Output generated from design level assessment to be feed into Global Ultimate Level Assessment (GUSA) if the structure fail to comply with the design level requirement.
GUSA comprises of three (3) integrated analyses which are Non-linear Plastic Collapse Analysis, Member Importance Analysis and Structural Reliability Analysis. These analyses will assist in quantifying the ultimate strength of the structure through Reserve Strength Ratio (RSR) and Probability of Failure (Pof). The outcome from the analysis can efficiently assist in understanding the structure failure mechanism and correctly defining type of mitigation required.
A few case studies is presented to give an insight on how this assessment is undertaken to demonstrate fitness for purpose of the structure and define the optimum mitigation measure.
Advanced Well Performance Analysis and Monitoring on Al Shaheen Field
Authors: Malakhov Denis , Gunningham Michael , Al-sadah Abdulla , Al-Suwaidi Abdulla 
Published: February 2015

An opportunity to establish a certain level of confidence in the well models by analysing entire production history or even performing analysis in real time becomes a reality of today. This paper is intended to describe an engineering approach to the analysis that was tailored to the Al Shaheen field to better understand the well performance, gain confidence in the models and identify various well issues and opportunities.
The challenge of understanding how wells perform is always associated with comprehensive data mining and significant time spent on analysis and calculations. However the data available is always limited and often requires quite a few assumptions to be made by an engineer when building a representative and reliable well model.
All industry standard software packages utilise same or similar well-known concepts and types of analysis from simple equations to more comprehensive algorithms. These are like pieces of the puzzle that can be assembled together to help petroleum engineer to get an idea of how the well should perform in particular circumstances. The way petroleum engineers applying these concepts on daily basis may vary depending on the nature of the problem they are facing and the amount of data they have available. Quite often the fact that the model does not match the reality is used to invalidate existing data and an opportunity to understand that something is happening in the well that is not captured by the model is overlooked. Reasons for this may include an existence of a particular purpose of the well model, level of engineer's experience, skills or imagination, lack of required data or at the end an inability to process the entire production data in an efficient way. The last becomes a real challenge on the fields with large amount of wells and extensive production history.
Synergy between adopted analysis and the technology has allowed engineers to gain a much better understanding of the well performance, identify various issues and opportunities and enabled them to keep focus on making decisions as to which wells to optimise and those to troubleshoot to maximise potential of the existing well stock.
Riser and Pipeline Corrosion Risk Assessment
Authors: Carr Peter 
Published: February 2015

When new tie-ins are made to existing infrastructure, corroded pipelines and risers may be subject to higher operating pressures than in their recent past. In order to help make informed decisions on whether such corroded components can be safely used at increased pressures, it is necessary to have a means of estimating their failure probability on introduction of the proposed higher operating pressure. A methodology has been developed to predict the probability of failure of a corroded pipeline or riser in the event of such an increase in operating pressure.
The application of the methodology to a 30-year old riser system containing several thousand corrosion clusters is described. The riser system comprised topside piping and a subsea tie-in spool as well as the vertical riser pipe. The analysis computed the probability of bursting if the pressure were to be elevated to a proposed new value. Using estimates of future corrosion rates, the analysis also estimated the remaining life of the system. The burst capacity model of DNV-RP-F101 was used, with allowance for the sizing accuracy of the inline inspection tool and for parameter and modeling uncertainties.
Two methods of computing the failure probability were explored:First Order/Second Order Reliability Method (FORM/SORM) andMonte Carlo Simulation (MCS). FORM and SORM are approximate methods, but very fast. MCS is an accurate method, but run times can be lengthy, particularly when the defect failure probabilities are low and when there are thousands of defects to analyze, as in the example case. As an exploratory exercise, FORM and SORM were tested against the MCS approach and found to have poor accuracy for this particular model. It was therefore decided to use MCS. The challenge in applying the MCS approach was then how to efficiently handle the analysis of thousands of corrosion clusters, each of which makes a small contribution to the overall failure probability.The paper describes how the MCS method was efficiently implemented and how the finished program was used to investigate sensitivity of the analysis results to different modeling assumptions, such as whether variables are treated as independent or correlated.
Rigless Stimulation in Deepwater Field - Case History: Jubilee Field
Authors: Rodriguez Jonathan , Hayford George , Kros Hans , Mancini Christopher , Bartlett Shawn 
Published: February 2015

Abstract
One the most common methods for well stimulation includes the use of mobile offshore drilling units (MODU) to pump fluids into the well with the main objective of restoring production or injection. A rig-based well stimulation is an expensive operation and in some cases a separate stimulation vessel is used to store and pump fluids. Economics to justify a stimulation operation may require a number of wells (depending on well productivity) to make the project economically viable. New industry developments in the last few years have made the use of special intervention techniques from vessels relatively popular. However, a riser based system remains the preferred method to intervene/stimulate deepwater wells. Riserless systems are becoming more and more popular but their applications vary from region to region based on water depths, sea conditions, equipment and technical personnel availability.
Since start of production from the Jubilee field, several oil producers had experienced gradual productivity decline with a significant reduction in flowing bottom hole pressure, despite an aggressive pressure maintenance program with water and gas injection. Following the success of previous acid stimulation work carried out off the rig in an attempt to restore productivity, a rigless acid stimulation treatment on the impaired Jubilee wells wasproposed. An initial feasibility study was conducted, whichindicated that a Rigless stimulation operations using a Multi Purpose Supply Vessel (MPSV) was considered to be a commercially and technically feasible operation. While the primary objective of the rigless stimulation campaign was to increase production, this work also demonstrated that the rigless intervention from the MPSV is a cost effective and technically feasible option for a long term campaign. The operation was successfully conducted using two vessels. Fluids where pumpd into the well using 4 × coiled tubing strings deployed in 1,600 m water depth. This paper explains the methodology used for the development of a rigless stimulation campaign in the Jubilee field, offshore Ghana.
High-Definition Resistivity Imaging of Low-Resistivity Formations Drilled with Nonconductive Mud Systems for Near-Wellbore Geological and Petrophysical Reservoir Evaluation
Authors: Le F. , Bal A.A. , Bespalov A. , Corley B. , Forgang S. , Gold R. , Itskovich G. , Gaafar G.R. 
Published: February 2015

A new wire-line formation resistivity imaging instrument employing a ‘two-electrode’ measurement configuration has been developed for application in low-resistivity formations drilled with non-conductive (oil-based) mud. A detailed explanation of the instrument and measurement principles is provided. Modeled synthetic responses and field examples are shown.
The high-spatial resolution of a ‘two-electrode’ arrangement has been well documented for nearly 25 years. The lower formation resistivity limit in oil-based mud boreholes for prior devices often precluded realizing their benefits in many important offshore deep water plays, such as Malaysia, Gulf of Mexico and elsewhere. The new instrument employs multi-frequency impedance measurements to overcome this limitation.
The impedance measurements produce two image logs: a real-part impedance image that is calibrated to yield formation resistivity and an imaginary-part impedance image that conveys information about image quality. The instrument employs six individually-articulated pads each containing ten sensor electrodes that provide a 75% surface coverage in an 8½ inch borehole. Typical spatial-resolution is better than one-half-inch vertically and one-eighth inch azimuthally. Pad-to-pad depth off-set is less than 6 inches, assisting to maintain borehole coverage in the presence of common instrument rotation during logging.
Field examples from typical logging environments found in offshore Malaysia are presented. Detailed geologic features such as thin-beds, slumping, cross-bedding, faulting and fracturing in low resistivity depositional environments are clearly resolved.