Volume 6: Polar and Arctic Sciences and Technology; Offshore Geotechnics; Petroleum Technology Symposium
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Published By American Society Of Mechanical Engineers

9780791855409

Author(s):  
Hannes Hofmann ◽  
Tayfun Babadagli ◽  
Günter Zimmermann

The creation of large complex fracture networks by hydraulic fracturing is imperative for enhanced oil recovery from tight sand or shale reservoirs, tight gas extraction, and Hot-Dry-Rock (HDR) geothermal systems to improve the contact area to the rock matrix. Although conventional fracturing treatments may result in bi-wing fractures, there is evidence by microseismic mapping that fracture networks can develop in many unconventional reservoirs, especially when natural fracture systems are present and the differences between the principle stresses are low. However, not much insight is gained about fracture development as well as fluid and proppant transport in naturally fractured tight formations. In order to clarify the relationship between rock and treatment parameters, and resulting fracture properties, numerical simulations were performed using a commercial Discrete Fracture Network (DFN) simulator. A comprehensive sensitivity analysis is presented to identify typical fracture network patterns resulting from massive water fracturing treatments in different geological conditions. It is shown how the treatment parameters influence the fracture development and what type of fracture patterns may result from different treatment designs. The focus of this study is on complex fracture network development in different natural fracture systems. Additionally, the applicability of the DFN simulator for modeling shale gas stimulation and HDR stimulation is critically discussed. The approach stated above gives an insight into the relationships between rock properties (specifically matrix properties and characteristics of natural fracture systems) and the properties of developed fracture networks. Various simulated scenarios show typical conditions under which different complex fracture patterns can develop and prescribe efficient treatment designs to generate these fracture systems. Hydraulic stimulation is essential for the production of oil, gas, or heat from ultratight formations like shales and basement rocks (mainly granite). If natural fracture systems are present, the fracturing process becomes more complex to simulate. Our simulation results reveal valuable information about main parameters influencing fracture network properties, major factors leading to complex fracture network development, and differences between HDR and shale gas/oil shale stimulations.


Author(s):  
Mario Zamora ◽  
Sanjit Roy ◽  
Kenneth Slater

The 1980’s introduction of costly non-aqueous drilling fluids finally sent the industry a wake-up call to seriously acknowledge the significant impacts of temperature and pressure on the downhole density and rheological properties of drilling fluids. Despite notable progress since then, key issues remain, mostly related to inherent complexities and uncertainties associated with quantifying these effects. Some issues are technical; others are procedural. Concerns are particularly critical on wells drilled under extreme HTHP (high-temperature/high pressure) conditions, in deepwater, and in Arctic and other ultra-cold locations. The primary objective of this paper is to discuss existing issues from well-integrity and wellbore-integrity perspectives, with focus on determining hydrostatic pressures and rheological properties under downhole conditions. Also included are new representative volumetric-behavior and viscometric data measured in the laboratory under extreme HTHP conditions.


Author(s):  
Omar Al-Farisi ◽  
Hadi Belhaj ◽  
Fatmah Yammahi ◽  
Abdulla Al-Shemsi ◽  
Hocine Khemissa

Rock typing is one of the most important steps in reservoir modeling, and it’s the main task in reservoir characterization. In carbonate, the rock typing work that’s been performed during the last two decades had a little progress in term of providing reliable estimation of reservoir behavior. However, the development of Conjunction Rock Properties Convergence, CROPC, a carbonate rock typing concept that provided an important and easy solution to the carbonate rock typing gaps, has a major breakthrough, even though, CROPC methodology was developed to capture the single pore network through the conjunction of Lithology, permeability, capillary pressure and water saturation. Therefore, the need to identify more complex carbonate pore network had led to the initiation of developing the Carbonate Rock Type Matrix RocMat, which will be detailed in this paper, as part of a Master of Science research project. In this novel concept the carbonate rocks were classified into homogeneous, single pore network, and heterogeneous rocks, dual and triple pore network with the utilization of the effective petrophysical properties of permeability, capillary pressure, saturation, porosity and height above free water level, all were classified in a conjunction matrix that honors these properties and at the same time enables generating sub groups as down scaling and estimation for unseen groups with infinite rock complexity capturing, at the same time it enables the ease to lump the groups and generates upscale-groups that make it easier for utilization by the geologist and reservoir engineers to achieve the objective of better reservoir performance prediction, the work was performed and then tested in two carbonate offshore fields data. This RocMat was structured to be the ultimate catalog for carbonate rock types.


Author(s):  
Basel Abdalla ◽  
F. Steven Wang ◽  
M. Kabir Hossain

The traditional method of foundation stability assessment for subsea structures is to calculate the bearing capacity factor of safety using classical approach given in the API-RP-2A/2GEO. This classical approach can be overly conservative for foundations under complex loading conditions (e.g., multiple interacting loads). A typical example is pipeline end manifold or flowline sled, which can be subject to self-weight, structure-soil interaction, and multiple interface loads from flowline and jumpers under operational condition. A more rigorous 3D-FEA based assessment approach is developed in this paper to achieve more accurate bearing capacity estimates for a flowline sled supported by mudmat. This fully combined global model comprises the structure (with sliding mechanism), soil foundation, jumpers, and flowline as realistically as possible so as to capture the more accurate interactions among the different parts of whole sled-soil system. The use of such advanced numerical modeling has proven to improve the mudmat bearing capacity factor of safety.


Author(s):  
Giovanni Spagnoli ◽  
Leonhard Weixler

Offshore piles are normally installed by driving using over-water or underwater hammers. However, there are many situations where pile reaches refusal before the installation depth. This paper briefly describes the current offshore foundation practice, the BAUER technology for onshore pile installation by drilling, the BAUER experiences in the offshore foundation and geotechnical fields and a new technology for supporting offshore pile installation when refusal is prematurely reached by means of the Dive Drill.


Author(s):  
Tor Einar Berg ◽  
Even Ambros Holte ◽  
Grethe Osborg Ose ◽  
Hilde Færevik

In this paper, we select some of the crucial issues for future search and rescue (SAR) operations in the Barents Sea. The different nations that are involved and the resources necessary to build emergency preparedness due to the climatic conditions are thus important factors. This paper summarizes the state of the art within these areas while also indicating future development needs. The special requirements for life saving equipment on vessels due to the climate and requirement on personal protective equipment related to accidental immersion are also essential and thus presented in this paper. In addition, safe haven designs where the vessel itself is designed to provide shelter for personnel in distress is also a topic chosen to be addressed.


Author(s):  
Darko Kupresan ◽  
James Heathman ◽  
Tao Tao ◽  
Mileva Radonjic

The focus of this novel research was to develop a physical model and apply an experimental approach to explore the effect of casing expansion technology on wellbore cement integrity.


Author(s):  
Josefine Michel ◽  
Patrick Kaeding

To mount service modules in a flexible manner on offshore platforms twistlock systems are used. If the application is not in accordance with standard conditions the existing regulations are not sufficient. Therefore new regulations with appropriate dimensioning equations must be generated. The results of the OMAE 2013 paper “Assessment of Container Mountings in Modular Offshore Platform Designs for Arctic Regions” are applied in this paper to reach such equations. The stress on twistlocks which mount standard containers to the offshore platform deck in arctic regions depends on roll angle of the offshore platform and friction coefficient — depending on temperature — and is analyzed by regression analysis in this paper. The results show that a local twistlock system can be used to simplify the calculation. Also the application of a crane module is simulated. The regression analysis is divided into two parts — the cone and the base of the twistlock: these parts take most of the load again depending on roll angle and friction coefficient. The result of this paper consists of dimensioning equations for these two different applications of twistlock systems in arctic regions.


Author(s):  
Alexander T. Bekker ◽  
Olga A. Sabodash ◽  
Roman G. Kovalenko

Characteristics of the drifting ice cover and the scenarios of the ice loads on offshore structures are the major parameters defining durability and reliability of the ice-resistant platforms on the Sakhalin offshore. The study is devoted to the problems of probabilistic and numerical modeling of the process of interaction between the ice cover and the ice-resistant concrete structures on the Sakhalin offshore zone. Geometry of the “Molikpaq” (PA-A) platform for Sakhalin-II Project is used as an example. The input statistical data were received on the basis of full-scale observations of the ice conditions in the Piltun-Astokhskoe deposit area during 1989–2002. The distribution of probability exceedance of ice loads for various ice scenarios on the “Molikpaq” (PA-A) platform was received. A probabilistic estimation of extreme values of ice loads was carried out, taking into account return period of ice conditions.


Author(s):  
Horst G. Brandes

The effectiveness of electromagnetic (EM), ground penetrating radar (GPR) and seismic refraction (SR) were evaluated by surveying a shallow trench in which a number of objects of varying composition and size were buried. The trench was excavated in granular calcareous fill material. An experienced geophysical contractor was asked to provide blind predictions of object locations using each of the techniques in turn. GPR with a 400 MHz antenna was the most successful, followed by SR and EM surveying. GPR and SR were also carried out at the port of Hilo to investigate complex subsurface conditions.


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