bluuebunny/crossref_metadata_2025_split huggingface dataset:
RasGas Rigless Drift Experience: New Technology and Evolving Best Practice - North Field, Qatar
Authors: Van Nuis Russell Robert , Mercer Larry , Morrow Timothy Ian 
Published: March 2015

Abstract
RasGas Company Limited (RasGas) operates a continuous and comprehensive Rigless well surveillance and monitoring program in the North Field, State of Qatar. The wellbores are designed to produce at high rates, therefore each well is a substantial asset and every intervention operation is critical to maintaining production capacity.
A drift operation is usually performed in each well to ensure logging objectives can be met safely. The normally unmanned offshore wellhead platforms (Fig. 1A) have limited deck space (Fig. 1B) which prevents simultaneous slickline and electric line operations.
Starting in 2007, RasGas deployed drifts on electric line, under certain conditions, using a 4.5-in. OD hollow carrier dummy perforating gun to ensure contingency fishing capability with a 4-in. OD overshot. Although this approach was favorable from a logistics, cost and schedule standpoint, the tool held-up in the perforations in three wells highlighting the risk of a lost tool and/or uncontrolled wire recovery, under high pressure sour conditions, due to a cable head weak point release.
Additionally, the surveillance program was delayed due to incremental drifting campaigns using mechanical wireline.
The paper will present RasGas drift experience and technical study results on the formation of perforation burrs and scale. Remediation of these obstructions should be a one-time event based on a study which indicates scale deposition is only expected to occur within the first few months of production. Additional discussion will include the development of two innovative slickline tools (De-burring Tool and Smart-Drift Tool) with significant advantages over conventional fixed diameter broaching/drift tools including a release mechanism to pull free from a stuck position.
The resulting optimized drift policy is based on an initial drift with a 5.75 in. OD Bell guide on mechanical wireline to ensure a successful latch of a 1-11/16-in. fishing neck. If wellbore remediation is required due to restrictions, the appropriate tools are selected based on the lessons learned described within the paper. After full wellbore access is established, future drifts can be performed safely on electric line using the new technology Smart Drift Tool to optimize logistics, cost and project schedule. The paper applies to other operators conducting cased hole logging programs and/or removing downhole perforation burrs or formation scale to meet well intervention objectives.
Anisotropic Imaging of Okubotin 3D, Onshore Niger Delta
Authors: Oni Adeboye Adebowale , Madiba Gislain B. , Ozumba Bertram Maduka 
Published: March 2015

Abstract
With the maturity of the Niger Delta region, having been producing hydrocarbons for the past fifty years, exploration has to look deeper to find any economic accumulations. Some of the consequences of looking deeper include the onset of overpressures and velocity anisotropy. One of the measures to counter these challenges in Onshore Niger Delta is the introduction of anisotropic prestack depth migration for all newly acquired long offset 3D seismic data.
The need to properly image the deep leads to acquisition of long offset data as in Okubotin 3D survey. The consequence is that Pre-Stack Depth Migration (PSDM) based on isotropic velocity model assumptions, though effective in imaging conventional reservoirs at shallower levels, is no longer adequate. The introduction of the long offset acquisition brings about a new challenge to derive an accurate velocity model to correct for the so-called 'hockey stick' effect at long offsets. Resolution of the velocity challenge helps in the better imaging of steep dips and corrects for non-hyperbolic moveout on Common Mid Point (CMP) gathers to give better image for the deep exploration plays in the field.
This paper presents a workflow for the use of anisotropic velocity model building in Okubotin area. It discusses the possible causes of anisotropy and the impact of anisotropic Pre-Stack Depth Migration processing of seismic data in Onshore Niger Delta. Results showed a much-improved imaging of the subsurface revealing new play potentials that were hitherto unknown in the area.
The successful imaging of the deep as in Okubotin 3D has enabled the development of a standardized workflow for this process, successfully unlocked the deep play in the Onshore Niger Delta by revealing impressive leads, explained the influence of anisotropy in the region and SPDC is now able to gain full dollar value of the legacy acquired long-cable seismic data.
Blended Learning: Finding the Right Mix
Authors: Oyetola George , Efana-Okon Essien 
Published: March 2015

Abstract
Globalisation and digitalization has impacted all spheres of organisational life including the process of deciding which learning technique and environment is most appropriate to meet training needs of employees. This changing trend has challenged management thinking from different facets; consequently today organisations are pondering effective modes of training and learning within their contexts. As an example, since their gradual departure from solely traditional training methods as their core training methodology; organisations are beginning to realise that e-learning is not a complete replacement for traditional learning. E-learning in many contexts represents radical change, within the oil & gas industry it may appear to be a very attractive training delivery option because of its time and cost efficiencies as well as its ability to remove geographic restrictions; however the complex nature of technical activities of oil and gas companies necessitates the use of traditional delivery methods. Social contexts of organisations must be taken into cognisance if they seek to radically change their learning management systems. Blended learning involves the mixing of several delivery techniques or methods of training in the appropriate proportions according to the unique need of each training program. The variety in composition means that providers can find greater opportunities in offering trainings that will improve learning outcomes. This paper adopts the standpoint that traditional HR processes and learning methods are effective, and that technology based learning requires further consideration by organisations. It introduces a blended learning model in action within a multinational organisation and argues an integrated approach to learning; that organisational learning must be aligned to culture, strategy and context.
Water Production Surveillance Workflow using Neural Network and Bayesian Network Technology: A Case Study of Bongkot North Field, Thailand
Authors: Hermann Roland , Nitura Jonathan Tabang , Ratanavanich Suvaluck , Chandakaew Rossawan , Iemcholvilert Sevaphol , Jiraratchwaro Chawiwan , Vitoonkijvanich Siriwat , Sarisittitham Sawatdiwong 
Published: March 2015

Abstract
The PTTEP-operated Greater Bongkot North Area of the Bongkot gas field is selected for the pilot with around 200 active production wells and four disposal wells. High water production from the gas wells impacts well performance negatively and water-handling capacity constraints limit the volume of produced water. This warrants in many cases the shutting in of erstwhile productive wells. Potential water producing wells are identified in a time-consuming process by monitoring every well manually based on well head temperature (WHT) and pressure (WHP) trends. This leads to a delayed identification of water production wells.
A new approach with a probabilistic predictive tool has been introduced for screening potential water production wells. A data mining approach with Self Organizing Maps and Bayesian Belief Networks is used in this case study. Well head data trends and well test data are used to train Neural Network and Bayesian Belief Network models to identify potential water production wells based on pre-defined trends. The end result is a probability of potential water production based on expert user knowledge and historical data trends.
Based on the potential water production probability, well tests are run to confirm water production. Using this tool, the user can justify running production logging tools (PLTs) to identify water-contributing zones and decide on water shut off measures that can be taken.
Self Organizing Maps and Bayesian Network models have been built for Greater Bongkot North. The predictability of the models was tested with historic data. The final models gave a reasonable success rate for detecting probable water production in wells. However, it was noted that knowledge of field behavior and extending the input data beyond the original well head data is required to further improve the prediction results.
It is planned to test the workflow later this year for selected Greater Bongkot North platforms to verify the applicability of the methodology in a live environment.

Introduction
Bongkot field is located 150 km off the eastern coast of Thailand, approximately 180 km North East of Songkhla Province, in a water depth of around 80 meters. The field is intensively faulted and gas is located in several sand bodies in depth between 800 and 2800 meter. The field started production in 1993 and was originally operated by TOTAL. Since 1998 PTT Exploration & Production Plc. (PTTEP) is the operator of Bongkot gas and condensate field in the gulf of Thailand. The field has been subdivided into two main areas, Greater Bongkot North (GBN) and Greater Bongkot South (GBS). Current Bongkot hydrocarbon production comes from Greater Bongkot North Area (GBN).
TTI RTM using Variable Grid in Depth
Authors: Dai Nanxun , Wu Wei , Zhang Wei , Wu Xiaofeng 
Published: March 2015

Abstract

Summary
In this abstract, we discuss some practical issues related to the implementation of reverse time migration (RTM) in a tilted transversely isotropic (TTI) medium. We have proposed a methodology to effectively reduce the cost. Through optimization of the coefficients of high-order difference scheme on the variable grid, larger depth steps at greater depth can be used instead of fixed step size. Synthetic data examples are used to demonstrate the effectiveness of the methodology.

Introduction
Reverse time migration (RTM) based on solving a two-way wave equation has been one of the most accurate imaging tools available in dealing with large lateral velocity variations and complicated geology such as large dips.
RTM for isotropic and vertical transversely isotropic (VTI) medium has been routinely in use in the industry, but the application of RTM in TTI medium is still in the early stage. This lag results from the difficulties in numerical formulations for non-vertical symmetric axes and the subsequent instabilities. The TTI implementation also leads to higher computational costs compared with its isotropic or VTI counterparts.
Instead of solving the original anisotropic wave equation, several modified quasi-P wave equations were derived by different authors, that can be used to perform anisotropic RTM for P-waves imaging without cause significant S wave scattering. Alkhalifah (2000) derived a 4th-order partial differential equation (PDE) in time to describe TTI propagation. To avoid solving a high order PDE, Zhou et al. (2006) split Alkhaifah's equation into two coupled 2nd-order PDEs. However it has been observed that their equations cause instability in practice when large dip is at presence. To circumvent this stability issue, Zhang et al. (2009) pursue an equivalent TTI formulation that preserves physical energy with the kinematics retained. Fletcher et al. (2009) proposed adding non-zero shear wave velocity terms to mitigate the instability problem. Unfortunately, their solution adds numerical complexity.
In our implementation, to deal with both the stability and accuracy issues in TTI environment, we have to cut the cost dramatically to run it in production environment. To reduce the computational cost of TTI RTM, we use the least-square-root method in the Fourier domain to construct optimized finite difference (FD) schemes of variable grid in depth to approximate the first and second order derivatives. With larger steps in space in deep layers of higher velocity while keeping the same criteria for controlling the numerical dispersion, the total number of grid point is reduced. We analyzed the stability condition for this proposed FD scheme to determine the size of time step, which is related to minimum grid space, maximum velocity as well as the coefficients of FD scheme. With this implementation our RTM has been enhanced greatly in efficiency, and gained success in numerous 3D land imaging projects. Here we will demonstrate the effectiveness of this method using the 2D BP TTI model as a test case.
Redefining a Sequence Stratigraphic Framework for the Miocene to Present in Brunei: Roles of Local Tectonics, Eustacy and Sediment Supply
Authors: Torres Jose A. , Gartrell Anthony , Hogg Nick 
Published: March 2015

Abstract
A Play Based Exploration (PBE) approach has been applied to the Brunei onshore, principle, second and third offshore agreement areas (OAA) of the Neogene (Serravalian to recent) deltaic sequences of the Baram - Balbac Basin operated by Brunei Shell Petroleum (BSP). Previous studies, utilizing a global sequence framework, are now considered to have underestimated the influence of local autocyclic forcing, manifested through high sedimentation rates, extensional delta-top tectonics and mutli-phase crustal shortening. Integration of shelf margin trajectories, biostratigraphy and structural kinematics has enabled a revised tectono-stratigraphic framework consisting of 10 major 3rd order sequences to be established in the Late Miocene to Present section. Regional compressional pulses are at the origin of some of these sequences, with syntectonic sequences showing onlap terminations on the flanks and/or thinning on the top of inverted structures and significant dislocations in the shelf edge trajectory.
A rigorous reassessment of the biostratigraphic framework has necessitated a revision of the sequence definitions and the synethsis of these observations is detailed. Two sequence boundaries are now calibrated to two major global eustatic falls (11.7 and 5.73 Ma). The 11.7 Ma event, a period of tectonic quiescence, is linked to a ~15 km basinward shift of the shelf edge trajectory without any clear sub-aerial erosion on the emerged shelf. The 5.73 Ma event, also a period of tectonic quiescence, is linked to a more modest basinward shift of the shelf edge, but accompanied by widespread canyon incision along most of the margin, and a major incision of the fluvial system feeding the Champion Delta.
Establishing a chronostratigraphic framework in deltaic sequences deposited on active margins requires a combination of pragmatism and caution. The same sequence may show very different stratal patterns and inferred systems tract along the same margin.
TTI/HTI Anisotropy for Fracture/Faults image inside Granite Basement
Authors: Zhou Ziqiang , Ngoc Nguyen Huy , Borthwick Tom , Zhao Kai , Teng Keat Huat 
Published: March 2015

Abstract
The oil-bearing, fractured granite basement rocks are a very important and complicated hydrocarbon reservoir in offshore Vietnam. However, the poor S/N ratio and imaging of these steeply dipping fractures by conventional Kirchhoff migration are quite difficult to interpret for exploration. The recent development of Controlled Beam Migration (CBM) has generated a much clearer fracture image inside the basement, but the velocity inside the basement remains an issue. The imaging velocity field needs to be much slower than the well sonic velocity to produce a decent fracture image.
With the help of the CBM stack sweeping technique, we have developed a new model building flow which takes into account the complex TTI/HTI anisotropy due to the micro-fracture system inside the basement. In this flow, the azimuthally dependant velocities for fractures are first picked through CBM stack sweeping; they are then compared with the well velocity trend to estimate the TTI/HTI anisotropy parameters. The azimuth angles are further updated by CBM stack sweeping with different azimuth angles.
The resultant seismic velocities much better fit the sonic velocity logs. Also, the migrated section has much less migration swings from multiples, and the imaging of the major fault/fracture system is enhanced. Azimuth angles of the TTI (velocity) model and the improved fracture imaging provide the much needed information for the "From Seismic interpretation to Tectonic Reconstruction" methodology, which has been proven to be effective in exploration in the Cuu Long Basin for the last five years (Ngoc et al., 2010).
The existence of TTI/HTI anisotropy inside the fractured basement is demonstrated through this case study. We have presented a new velocity modelling flow which can estimate the azimuth information for fracture systems and improve the imaging quality inside the basement.
Interorganizational Relation: A Key Factor for Maintenance Contract Success
Authors: Limsoonton Tawee 
Published: March 2015

Abstract
Though most of maintenance functions in the Oil and Gas business usually adopt the Contract Out philosophy which is under the concept of Specialization, it does not always guarantee for success. Because E&P business usually focuses on their core business in finding and developing oil production but the maintenance activities of its operating asset are aside as a support and cost center activities. Also the E&P believes that the specialist from external could do it better both in terms of efficiency and budgetary.
This concept is acceptable if all related departments are in a good mechanism and structuring from top to bottom of the contractor's organization or from one side to the other side of the owner and contractor. But in the real world, Sirikit Oilfield (S1) has experienced poor performance of contractor because of unaligned target of the company and contractor, low competency of contractor staff, high turnover, and slow response.
To solve these problems, S1 develops maintenance organization under the 'hybrid' concept which covered under the Interorganizational Relation (IOR) paradigm. Then IOR is theoretically based upon that all of organizations are located in the environment and affected by their environment and vice versa. Then one organization is able to cause any direct and indirect effect to the other. Under the environment of contract condition, one organization performance also affects the other one's performance no matter if they are owner or contractor. The competency and management system of S1 maintenance staff does not affect only to its own performance but also the performance of the contractor.
This concept delimits any incompetent of the contractor by transferring any work control of the contract staff to be under the accountability of S1 own staff. On the other hands the contractor will be responsible for competency management and benefit-compensation management.
Since 2007 which this concept has been introduced, the achievement of contractors' KPI improves from 74.4% in 2008 to be 98.2% in 2009. SSHE activities score at 86%, Inspection Compliance / CM- PM Compliance &gt; 95%.
Developing a Stage Tool for Cemented Back Monobore Completions with Open Hole Multi-Stage Systems in the Montney
Authors: Kimmitt Kyle Patrick 
Published: March 2015

Abstract
Challenges associated with cementing horizontal wellbores, as well as the higher operational time and costs associated with the cemented liner, plug and perf method, has resulted in many operators switching to open hole multi-stage system (OHMS) completions. In addition, production increases have been realized with OHMS due to access to the entire open hole lateral.
To further optimize economics, cemented back monobore completions with OHMS are becoming the completion method of choice for operators. This is because they save on wellbore costs by eliminating the intermediate casing. Instead, the build section of the wellbore is cemented back to surface using a stage tool once the liner is installed. In addition, the cemented back method allows for OHMS systems to be run in on liner eliminating the need to trip out the running string and trip in the frac string.
This paper outlines the operational procedure for cemented back monobore OHMS completions. Due to various issues with conventional plug-type cementing stage tools a new hydraulically activated, mechanically closed cementing stage collar was designed to open/close without the use of a plug/dart. The new stage tool addresses the operational issues encountered with conventional tools and further reduces costs by reducing rig time. With the new stage collar, there is no drill out of plugs and cement after the cementing operation, eliminating debris that could be problematic for the OHMS functioning.
The development of the new stage collar through lab testing and field trials is discussed. This technology has been successfully used in various formations in Canada and the United States. This paper presents case study examples of installations in the Montney formation.

Introduction

Geology of the Montney.
The Montney formation covers an area of approximately 246,000 km2 (95,000 sq. mi.) stretching across Alberta and British Columbia (Figure 1). It is a leading example of an unconventional gas play in the Western Canadian Sedimentary Basin containing vast quantities of proven gas reserves. Estimates of gas in place are up to 700 Tcf.
The Montney consists of four distinct intervals: the Upper, Middle, Middle Lower and Lower (National Energy Board, Canada). Characterized by its low permeability (0.01 - 0.5 mD) and thick stack, the Montney is a prime candidate for horizontal drilling and hydraulic fracturing techniques. The formation is a blend of sandstone, siltstone and shale intervals with porosity up to 8% and true vertical depth to 3,950 m (13,000 ft).
Evaluation of Stress Anisotropy of the Formation by Utilizing Dipole Shear Sonic Imager (DSI*), Formation Micro Imager (FMI*) and Density logs. A Case Study on Kanawara Field, South Cambay Basin, India.
Authors: Pachineelam Subrahmanyam , Paluri Bharat Sactry , Mudigonda Anand Siva Kumar , Jagannadha Rao Nagavaradu Dharma 
Published: March 2015

Abstract
Knowledge on Stress anisotropy of the formation is vital to understand the stress direction and magnitude. A stress direction allows well bore stability analysis for safe and cost effective drilling in a challenging environment. Well bore stability analysis showed a large tectonic imbalance between minimum and maximum horizontal stress. As a result, wells drilled in the direction of maximum horizontal stress will have a significant increase in wellbore stability problems compared to those drilled in the direction of minimum horizontal stress. Perforations to be oriented consistent with stress direction to optimize the production and minimize sanding problems. Identification of anisotropy due to fractures leads to enhanced production and maximize the oil recovery from the hydraulic fracturing job.
Well bore stability analysis (WBS) of Kanawara field can be performed by define the rock properties such as Young's modulus, Shear modulus, Poisson's ratio and elastic properties like unconfined compressive strength (UCS) and friction angle of the formation. WBS is a numerical representation of rock mechanical properties, in-situ stresses and pore pressure for a specific stratigraphic section in a field. Compressional slowness (DTCO) and shear slowness (DTSM) along with density (RHOB) log are basic wireline measurements used in determining formation mechanical properties in the vicinity of well #1.
The geomechanical study was conducted by utilizing data from all domains, which included wireline data mainly Dipole sonic (DSI*), FMI* and Density logs. Drilling and completion reports, mud logs, MDT tests, minifracture tests, injectivity tests and LOT values are used for calibration purposes.