No description available.

A multidisciplinary approach combining thin section and whole rock geochemical analyses has been used to investigate and characterise the Bilinguites gracilis marine band (Marsdenian, Carboniferous) and the fine-grained succession that includes this horizon. The lithofacies, geochemical signatures and organic matter distribution (TOCcalc) are examined from proximal (Brough, Cumbria) and distal (Oakamoor, Staffordshire) successions, relative to main sediment source, across the Pennine Basin. Clay-rich homogeneous mudstones dominate the more proximal succession and contain evidence of intense bioturbation which significantly modified the original fabrics. These bioturbated mudstones are characterised by low abundances of redox-sensitive trace elements (e.g. molybdenum (<1.8 ppm) and uranium (<4.5 ppm)), reflecting deposition in an oxygenated environment. Clay-rich mudstones with a lenticular fabric dominate the distal succession and have much higher abundances of redox-sensitive trace elements (e.g. molybdenum (up to 205 ppm) and uranium (up to 25.1 ppm)). The preserved lenticular fabrics, containing faecal pellets from benthic deposit-feeders, are interpreted to result from more rapid deposition and burial, reducing the influence by bioturbation. The fabrics (matrix-supported 3-D preserved goniatites (lower leaf) and sub-millimetre graded beds (upper leaf)) in the Bilinguites gracilis marine band indicate that debris flows (lower leaf)and turbulent flows (upper leaf) were the main depositional mechanisms, contrasting with the traditional interpretation that marine bands were deposited slowly by suspension settling. Proximally TOCcalc is typically less than 2%, due to organic matter degradation in a better oxygenated environment (e.g. clay-rich homogeneous mudstones contain <2%). TOCcalc abundances are higher in the distal location, up to8.9%TOCcalc, which reflects less destruction by bioturbation and enhanced preservation due to more rapid burial(e.g. clay-rich lenticular mudstones and carbonate-rich bedded mudstones contain >2%). Therefore, understanding mudstone characteristics (fabric and geochemical signatures) is important to assessing where the organic matter may be concentrated in a potential shale gas play and why.

Tight gas-condensate reservoirs contain large reserves, but can be extremely costly to develop. Understanding the fundamental controls on the fluid flow behaviour of tight gas and gas-condensate reservoirs has the potential to result in more cost-effective reservoir development and help increase the world's producible reserves. Therefore, the principal objective of the thesis is to improve understanding of multiphase flow within tight gas-condensate reservoirs. In order to achieve this objective a series of pore-to-core scale experiments under controlled conditions were performed, followed by numerical simulation. Three methodologies were used in this study: First, pore-scale experiments in glass micromodels with liquid-liquid systems were performed to improve understanding of the phase separation and flow mechanisms at pore level. Second, coreflood experiments were performed while in-situ saturation was monitored using an X-ray C'I' -scanner. A newly developed liquid-liquid system was used in these experiments. Flow through tight gas sandstones allowed the determination of relative penneabilities as well as determining their dependence on absolute permeability and capillary number. Third, production simulation modelling has been conducted to investigate the implications of the results. The micromodel experiments have proved extremely useful for characterizing the flow behaviour . of condensate systems. The results showed that the flow mechanisms and phases' distributions were affected largely by interfacial tension, pore structure and wettability.

Tight sandstones are becoming an increasingly important source of natural gas due to a combination of increased demand and decline in production from conventional reservoirs. Tight gas sandstones have vast quantities of gas which can extend for thousands of square miles, yet there are many problems that encounter the production from these reservoirs. For example, the production rate is not only low relative to that in conventional reservoirs, but drops dramatically with increasing the total effective stress. In addition, tight reservoirs have very low permeability (poor reservoir quality) and the identification of sweet spots (regions of high fracture density) is of great importance. This research, firstly, explores the stress dependence of tight sandstones properties mainly the stress dependence of gas permeability (absolute, effective and relative) and the stress dependence of ultrasonic velocity (dry and water partially saturated), in addition to microstructural analysis. Secondly, a finite difference wave propagation code, WAVE, is used to highlight the seismic attributes which can be used to detect sweet spots. Microstructural analysis indicated that tight sandstones have variable microstructure where the microstructure of some tight samples is characterized by isolated pore spaces and narrow pore throats (may exhibit crack like shapes). Low porosity « 10%), low permeability « 0.1 mD) samples are found to be more permeability stress sensitive than high porosity, high permeability samples. It should be emphasized, however, that laboratory measurements conducted at low stress conditions (~ < 3000-4000 psi) might overestimate in situ stress changes. This is because microcracks density develops during coring (stress release) and stress changes at low stress conditions are likely to be related primarily to changes in microcracks aspect ratio. In an attempt to correlate stress changes of permeability to that of ultrasonic velocity, the results showed quite broad scatter and there is no quantitative measure between the stress sensitivity of permeability to that of ultrasonic velocity. Using finite difference wave propagation modelling, scattered waves (e.g. P-S converted waves and/or Rayleigh waves) might be a potential seismic attribute in the detection of sweet spots.

No description available.

Identified as an important issue for marginal fields, the removal of sand from hydrocarbon fluids has been investigated. A review of existing sand separation equipment has recognized a need for a new separator which will satisfy the design and performance requirements necessary for protecting offshore processing equipment. This thesis details the work and analysis undertaken which has contributed towards the design and development of a new offshore gas/solid separator. A critique of different separation techniques has identified axial flow cyclone (AFC) separators as a suitable separator design for offshore desanding applications. After reviewing existing models which simulate the performance of AFC separators a simple classification table has been developed. Using the conclusions of this review as a starting platform, a methodology for developing a new computational fluid dynamics (CFD) performance model for the new separator was proposed. Experimental work undertaken at the CALtec laboratories and the BG plc (formerly British Gas Research and Technology) Low Thornley test facilities are presented. The results obtained have been used to analysis the performance of difference separator internal designs. In addition, the results have been used to evaluate the robustness of existing AFC performance models and validate the new CFD model. For the investigated operational duties, the new CFD model has been shown to consistently under-predict the collection efficiency, whereas the other AFC models over-predict. From a design point of view, a model which under-predicts the overall collection efficiency will result in the over-design of the separator for a particular operating duty. Therefore, the use of such a model will ensure the design of a separator which will offer greater than expected levels of protection of downstream equipment from erosion wear.

No description available.

No description available.

No description available.

The void space properties of a set of gas reservoir sandstone samples have been measured. The properties include porosity, absolute gas permeability, electrical resistivity formation factor and tortuosity. The mineralogy of each sandstone was determined by scanning electron microscopy and energy dispersive x-ray analysis. Mercury intrusion and extrusion data have been measured for most of the sandstone samples. A new procedure for measuring the degree and range of void size correlations within resin-filled sandstones has been developed. Image analysis of backscattered electron micrographs of these samples supplies void size and positional information. A &quot;semi-variogram&quot; study of void size and coordinate data ascertains the degree and range of void size correlation. Measurable correlation has been found in two sandstone samples, but was absent from four others. Diffusion coefficients of methane, iso-butane and n-butane through dry sandstones have been measured using an adaptation of a non-steady state method, using a redesigned apparatus. A repeatability and error analysis of diffusion coefficient measurement has also been performed. A correlation between diffusion coefficients, absolute permeability, porosity and formation factor was detected for sandstones containing little clay. The diffusion coefficients measured for clay affected sandstones did not correlate with any petrophysical properties of these samples. A computer model capable of simulating porous media has been previously developed. It consists of a 10x10x10 network of cubic pores and cylindrical throats, and simulates die mercury intrusion curve. The void size distribution is modified until both simulated and experimental curves closely match. New void size distribution input and curve fit algorithms have been developed to increase the speed and accuracy of die simulations and a new modelling procedure allows the modelling of samples with void size correlation. The model is capable of simulating porosity, permeability, tortuosity and mercury extrusion. Each of the reservoir sandstones has been modelled and their characteristic properties simulated. Successful simulations were obtained for all relatively clay-free reservoir sandstones. Clay affected sandstone simulations were less successful due to the high complexity of these samples. A study into formation damage witiiin reservoir sandstones was also undertaken. The effect of colloidal particulate void space penetration is measured and simulated.