Copyright 2019 held jointly by the Society of Petrophysicists and Well Log Analysts (SPWLA) and the submitting authors. ABSTRACT Today, many machine learning techniques are regularly employed in petrophysical modelling such as cluster analysis, neural networks, fuzzy logic, self-organising maps, genetic algorithm, principal component analysis etc. While each of these methods has its strengths and weaknesses, one of the challenges to most of the existing techniques is how to best handle the variety of dynamic ranges present in petrophysical input data. Mixing input data with logarithmic variation (such as resistivity) and linear variation (such as gamma ray) while effectively balancing the weight of each variable can be particularly difficult to manage. DTA is conceived based on extensive research conducted in the field of CFD (Computational Fluid Dynamics). This paper is focused on the application of DTA to petrophysics and its fundamental distinction from various other statistical methods adopted in the industry. Case studies are shown, predicting porosity and permeability for a variety of scenarios using the DTA method and other techniques. The results from the various methods are compared, and the robustness of DTA is illustrated. The example datasets are drawn from public databases within the Norwegian and Dutch sectors of the North Sea, and Western Australia, some of which have a rich set of input data including logs, core, and reservoir characterisation from which to build a model, while others have relatively sparse data available allowing for an analysis of the effectiveness of the method when both rich and poor training data are available. The paper concludes with recommendations on the best way to use DTA in real-time to predict porosity and permeability. INTRODUCTION The seismic shift in the data analytics landscape after the Macondo disaster has produced intensive focus on the accuracy and precision of prediction of pore pressure and petrophysical parameters.
Chullabrahm, Pattarapong (PTT Exploration and Production Public Company Ltd) | Saranyasoontorn, Korn (PTT Exploration and Production Public Company Ltd) | Svasti-xuto, Maythus (PTT Exploration and Production Public Company Ltd) | Trithipchatsakul, Chao (PTT Exploration and Production Public Company Ltd) | Sunderland, Damon (Arup Pty Ltd) | Ingvorsen, Peter (Arup Pty Ltd) | Madrigal, Sarah (Arup Pty Ltd) | McAndrew, Russell (Arup Pty Ltd)
This paper presents an integration of geology, geohazards, geophysics and geotechnical assessments for a design of an offshore gas production facility and an associated export pipeline. The gas field described in this paper is located off the North West coast of Australia in the Timor Sea in a water depth of approximately 130m.
Various resource development options were investigated during the Concept Select / pre-Front End Engineering Design (pre-FEED) phase of the project. These options included fixed and floating structures in the infield area and a 300km long export pipeline that ties into an existing gas trunkline connecting to an onshore processing plant.
To provide the necessary engineering due diligence to allow the project to progress further, several phases of geo-related investigations were undertaken to assess various geohazard challenges and foundation risks. Some of these challenges include a pipeline route traversing several steeply sloping seabed canyons, potential activation of turbidite sequences, and the presence of very soft carbonate sediments to calcarenite rock.
This paper describes these ground related challenges and how they were constrained through the geo-related investigations conducted, observations made and results obtained. Ground related challenges are described in two parts: Pre-FEED export pipeline routing reviews focusing on geohazard, geophysical and geotechnical considerations and ‘real time’ pipeline engineering Finite Element Analysis (FEA) performed offshore. Compared to normal practice, this non-standard offshore analysis allowed a preferred pipeline corridor to be identified during the survey with an informed understanding regarding feasibility and likely seabed intervention, thus optimising the field survey time and cost; and Staged acquisition and integration of infield geophysical and geotechnical data for developing high level assessments of foundation concepts.
Pre-FEED export pipeline routing reviews focusing on geohazard, geophysical and geotechnical considerations and ‘real time’ pipeline engineering Finite Element Analysis (FEA) performed offshore. Compared to normal practice, this non-standard offshore analysis allowed a preferred pipeline corridor to be identified during the survey with an informed understanding regarding feasibility and likely seabed intervention, thus optimising the field survey time and cost; and
Staged acquisition and integration of infield geophysical and geotechnical data for developing high level assessments of foundation concepts.
Key benefits of conducting an integrated approach to geo-related challenges on a complex site will also be presented in this paper.
The selection of completion equipment for artificial lift string for any field in the oil and gas industry is important for the safe and reliable operations of such a field. This is critical to the management and overall profitability of the oil and gas asset, especially in areas where artificial lift is the predominant means of water injection and hydrocarbon production. This paper focuses on why it is important to understand the saline subsurface and the total dissolved solids (TDS) of the environment in which the artificial lift completion is to be deployed and its impact on equipment selection.
High concentration of corrosive components in the well fluid such as hydrogen sulfide, chlorine and total dissolved solids makes the well fluid conducive for electron migration. Such migration causes heavy corrosion, especially when dissimilar metals are used in artificial lift well completions. Carbon steel tubulars and casing are easily affected by such corrosive composition and leads to premature failure of artificial lift completions, which poses safety and operational issues. This type of environment is intense in electrical submersible pump completed wells because of the electromagnetic field generated by the current passing through the electrical cable of the pump system.
A combination of field and laboratory data gathering, and analysis was utilized to determine the effect of the aggressive components of the produced fluid on electrical submersible pumps assembly. The contributions of the high total dissolved solids in the conductivity of the well fluid, and in the electrochemical process for metal corrosion were analyzed. It was evident from both forms and approaches utilized in the analysis that well fluid becomes an electrolyte that provided the desired path for electron flow, which was enhanced by the magnetic field of the ESP system cable.
This paper highlights the integration of three approaches of geochemical analysis of well effluent, Anodic Index differential and tubular internal coating in corrosion prevention and electric submersible pump runlife elongation in wells with corrosive compositions including high total dissolved solids.
Each module has a duration of two days with emphasis on different aspects of reservoir characterisation, the ultimate goal being the preparation of optimal formation and rock property data from core analysis and other data sources for the purpose of static geological modelling and dynamic reservoir simulation. Seminar style lectures are typically given each morning and participants put their learning into practice in the afternoons, utilising real field data (including their own if desired). For this purpose, specialised spreadsheets are utilised. "Intelligent" spreadsheets will be made available to course participants for their use in practical exercises – putting theory into practice. Course participants may also bring their own data, which they may use with the spreadsheets.
Advanced levels of depletion cause unexpected reduced pore pressures and thus reduced reservoir fracture gradients, presenting considerable drilling challenges in the Burgan Field in Kuwait. This can lead to matrix damage due to mud losses and result in borehole collapse due to the relative increase of effective stress concentration in the vicinity of the borehole. The area of the study showed high levels of non-productive time (NPT) as well as increased costs due to the drilling of unplanned sidetracks in highly deviated wells. LWD Penta-combo measurements including azimuthal sonic and formation pressure have been utilized to model fracture gradient and borehole collapse gradient in real-time, and proved effective at reducing risks and rig time by allowing proactive management of these challenges.
Borehole collapse in offset wells was analyzed to predict and simulate the wellbore stability of a planned well via a pre-drill geomechanics model prior to drilling the well. The well was planned with a high deviation of 56° and oil based mud. The salinity of the water phase was recognized as an essential factor in assessing wellbore stability risk with respect to shale-dependent time failure.
The integration of real-time LWD sonic and density data with formation pressure testing data in the geomechanics model for the first time in the 12 ¼-in. section showed excellent correlation and confirmed different levels of depletion in the reservoir. Uncertainty in the modeled fracture gradient was significantly reduced and effectively eliminated with the inclusion of real-time formation pore pressure testing data. This successful combination of modeled pore-pressure curves from the real-time LWD sonic data with the real-time formation pressure test data acquired while drilling in the same run is a first in Kuwait. A total of 15 pressure points were sampled in real time while drilling, allowing for proactive mud window optimization and borehole stability geomechanical analysis.
This real-time wellbore stability technique based on advanced LWD azimuthal acoustic technology in conjunction with real-time formation pressure testing while drilling has been developed with a unique process and workflow allowing the operator to drill the well with no significant wellbore stability issues and with the optimized shape of the borehole for a safe casing run. In addition, NPT was reduced to 0 hours and overall days per well were reduced significantly.
Behrenbruch, Peter (Bear and Brook Consulting) | Hoang, Tuan G (University of Adelaide) | Do Huu, Minh Triet (Bear and Brook Consulting) | Bui, Khang D (Bear and Brook Consulting) | Kennaird, Tony (Bear and Brook Consulting)
Dynamic reservoir simulation models are used to predict reservoir performance, and to forecast production and ultimate recovery. Such simulation models are also used to match historic production. The success of such models depends critically on optimal gridding, particularly vertical definition and the choice of rock parameters, especially relative permeability.
This paper compares simulation results as a function of utilising alternative relative permeability relationships as simulation input:
Unaltered laboratory data Modified Brooks-Corey ( Relationships based on the more recently derived two-phase Modified Carman-Kozeny (
Unaltered laboratory data
Modified Brooks-Corey (
Relationships based on the more recently derived two-phase Modified Carman-Kozeny (
For maximum clarity, comparisons are made on a single layer basis but covering a range of permeability and porosity values, and capillary pressure relationships are based on modelled lab data using the Modified Carman-Kozeny Purcell (
Study results show that very different production responses may be realised, depending on the validity of original lab data and choice of modelled relationships deployed. It is concluded that the use of the
This paper presents an advanced method to accurately calculate oil and gas production from the Laminaria and Corallina fields produced by the Northern Endeavour FPSO on the Timor Sea, where direct metering has become unreliable or unavailable. The entire production data history was reconstructed, and results applied for better understanding of the reservoir and enabling better facility planning.
The newly developed allocation methodology is based upon PVT correlations that map liquid/gas ratios from production separator conditions to plant products. Mass balance at component level was applied to ensure sources and uses of gas + LPG were fully accounted for. Instead of the conventional approach where a simple oil shrinkage is applied, this method accounts for oil shrinkage which varies with process operating parameters, gas lift rate and back produced gas. The light oils from the Laminaria and Corallina fields are particularly susceptible to these effects.
Before any reconciliation, the total oil from these two fields calculated by this independent method compares closely with cumulative field life exported oil, and monthly reconciled rundown. Oil allocations between fields were rebalanced based on the mass allocation approach. Additionally, gas production figures were affected after discovering that a significant quantity of previously injected gas + LPGs had not been back-produced and was instead captured in the reservoir flow path. The reallocated production data and improved metering of current gas and LPG production rates enables a more representative reservoir model of remaining oil, gas and LPG ultimate recovery, well free-flowing limits, timing for infill wells and evaluation of the potential for alternate fuel availability based on mass reallocation of LPGs.
Insights from this work have provided key inputs into decisions on facility modifications and upgrade projects to maintain production and extend field life. The correlations and the workflow from this work have also been programmed into the Process Historian Database for better real-time monitoring and automation. The methodology described is applicable to other light oil or gas condensate fields to significantly improve metering, leading to better reservoir understanding and facility planning.
In an era of automated workflow-assisted dynamic modelling, Special Core Analysis (SCAL) parameters require updating for each static realisation and evaluation at a quantifiable, probabilistic level-of-certainty. Additionally, SCAL data gaps combined with limited reliable SCAL data drive the need to establish trends and correlations from analogues.
SCAL parameters from analogue fields were selected and filtered by depositional environment and laboratory experiment type (centrifuge versus displacement). These analogue SCAL parameters were allocated to statistical bins defined by absolute permeability ranges. Statistical analysis of each SCAL parameter allocated to each permeability bin produced a probability distribution discretised by percentile. Multi-variable linear regression (MVLR) was then implemented to correlate each SCAL parameter, as the response variable, to input variables absolute permeability and percentile. SCAL correlations of reasonable to excellent quality were obtained.
The depositional environment was of second order influence in establishing these SCAL correlations. This was due to the selection of core plugs for laboratory analysis from layers of similar quality irrespective of the depositional environment, highlighting the need to select samples characterising a range of lithology and reservoir quality. Centrifuge experiments of water displacing gas were discarded as unreliable due to the compression of the gas phase by the experimental technique.
The multi-variable linear regression methodology enabled SCAL parameters to be determined as a function of both absolute permeability and probability. This approach should enable an automated implementation of SCAL parameters within each dynamic model realisation.
Australia is uniquely positioned globally as a major energy provider, but this comes with multiple challenges that must be overcome to realize its full potential. LNG developments that are nearing fruition are set to make Australia the largest supplier of LNG in the world. The Asian LNG market continues to be the growth market. The development of the world's first coal bed methane (coal seam gas) to LNG projects on the east coast has created a robust east coast LNG export market, which in the near future is expected to coincide with domestic energy shortages arising from low exploration activity, maturing fields, higher costs, the interaction of government policy, commercial decisions and activism. As a result, unique approaches to project management and community relations have been developed that are complementary to the Australian consumer's needs for reliable, affordable and cleaner energy. The east coast demand for gas is likely to trigger new development of onshore Northern Territory gas in the short term, if political opposition can be managed. In Western Australia, new approaches leverage technologies such as floating LNG, and more utilization of existing infrastructure and plant capacity to achieve lower costs. This paper outlines Australia's natural gas supply & demand and the challenges to be faced in the coming years.
Dubinya, Nikita (Schmidt Institute of Physics of the Earth, RAS) | Trimonova, Mariia (1) Institute of Geosphere Dynamics RAS) | Tyurin, Alexander (2) Keldysh Institute of Applied Mathematics RAS) | Golovin, Yuri (Center of Nanotechnology, Derzhavin Tambov State University) | Zenchenko, Evgeny (Center of Nanotechnology, Derzhavin Tambov State University) | Samodurov, Alexander (Institute of Geosphere Dynamics RAS) | Turuntaev, Sergey (Center of Nanotechnology, Derzhavin Tambov State University) | Fokin, Ilya (Institute of Geosphere Dynamics RAS)
The article is devoted to mathematical and physical modeling of the process of hydraulic fracture initiation and propagation in the material with known physical-mechanical properties. Fracture toughness was the main focus of the research as it is a parameter characterizing the rock's ability to resist fracturing process. This parameter alongside with rock elastic properties and pumping conditions is one of the governing parameters while considering the fracture propagation in terms of mechanics of brittle fracture. The study is aimed at understanding the impact of fracture toughness on geometric properties of a fracture by means of numerical modeling of laboratory experiments of hydraulic fracture propagation in a model material. The strength properties including fracture toughness of the used model material have been studied using the indentation methods. The difference between experimentally observed and numerically calculated (keeping in mind the estimated strength properties) fracture geometry is studied in the paper and the possible reasons for this difference are discussed.