During production operations in heavy oil and bitumen formations where thermal recovery methods are applied, the fluids produced are often in the form of emulsions. This is also true in non-thermal recovery methods whenever oil and water are coproduced, but to a lower degree of severity. Conventional flow measuring devices are capable of measuring oil and water streams when they are segregated, but they fail when oil-in-water or water-in-oil emulsions form. Conventional methods are also not reliable when there are solids flowing in the stream. Low field NMR relaxometry was successfully tested as a tool for accurately measuring the oil and water content of such streams with and without emulsions present in the samples. The method was proved to be at least as good as conventional extraction methods (i.e., Dean-Stark). The technology was tested with both artificially and naturally occurring emulsified streams with accuracy better than 96﹪. This extremely encouraging result led to the design of an online NMR relaxometer for oil/water stream measurements under the conditions encountered in the production of heavy oil and bitumen. Introduction In the recovery of bitumen, viscosity reduction becomes important, both below and above the ground. The addition of a liquid diluent is thought to break down or weaken the intermolecular forces which create high viscosity in bitumen(1). The effect is so dramatic that the addition of even 5﹪ diluent can cause a viscosity reduction in excess of 80%; thus, facilitating the in situ recovery and pipe line transportation of bitumen. The knowledge of the bitumen-diluent viscosity is highly important, since without it, calculations in upgrading process, in situ recovery, well simulation, heat transfer, fluid flow, and a variety of other engineering problems would be difficult or impossible to solve. This paper presents the development of a simple correlation to predict the viscosity of binary mixtures of bitumen-diluent in any proportion. Experimental The data used for the development of the correlation was TABLE 1: Bitumen data at 30 °CDATA[C. Available In Full Paper. TABLE 2: Diluent data at 30 °CDATA[C. Available In Full Paper. obtained from Wallace et al.(2) and Wallace and Henry(3).The data consisted of a total of 99 points obtained from three bitumens and five diluents, respectively, listed in Tables 1 and 2. Each of these bitumen samples was diluted at 30 °CDATA[C to 5, 10, 25, 50 and 75 weight ﹪ diluent with each of the diluents. After mixing, the samples were reweighed, and any weight loss was attributed to solvent evaporation. The diluent weight fractions were adjusted accordingly, and the viscosities of the mixtures measured. For a detailed account of experimental procedures, refer to Wallace and Henry(3). Correlation Development Many correlations have been developed to predict the viscosity characteristics of bitumen-diluent mixtures(1-6). While several have been successful in making these predictions, most are cumbersome to use. Low Field Nuclear Magnetic Resonance (NMR) relaxometry techniques were developed in the laboratory to enhance and support comparable NMR logging tools that are currently used downhole.

Enhancing oil extraction from oil sands with a hydraulic fracturing techniquehas been widely used in practice. Due to the complexity of the actual process, modelling of hydraulic fracturing is far behind its application. Reproducingthe effects of high pore pressure and high temperature, combined with complexstress changes in the oil sand reservoir, requires a comprehensive numericalmodel which is capable of simulating the fracturing phenomenon. To capture allof these aspects in the problem, three partial differential equations, i.e., equilibrium, flow, and heat transfer, should be solved simultaneously in afully implicit (coupled) manner. A fully coupled thermo-hydro-mechanical fracture finite element model isdeveloped to incorporate all of the above features. The model is capable ofanalyzing hydraulic fracture problems in axisymmetric or plane strainconditions with any desired boundary conditions, e.g., constant rate of fluidinjection, pressure, temperature, and fluid flow/thermal flux. Fractures can beinitiated either by excessive tensile stress or shear stress. The fractureprocess is simulated using a node-splitting technique. Once a fracture isformed, special fracture elements are introduced to provide in-planetransmissivity of fluid. Effectiveness of the model is evaluated by solvingseveral examples and comparing the numerical results with analytical solutions.The model is also used to simulate large-scale laboratory hydraulic fracturingexperiments. Introduction Hydraulic fracturing technique has been a fast growing technology since itsfirst application in 1947. By 1988, more than one million hydraulic fracturingtreatments had been performed(1), and today this technique is one ofthe most important methods in enhancing oil extraction from wells. Hydraulicfracturing in oil and reservoirs plays an even more important role. Due to lowtemperature and low permeability of oil sand deposits and high viscosity ofbitumen, oil is virtually immobile(2). Hence, any attempt for insitu oil extraction should employ one of the following techniques: cyclic steamstimulation, in situ combustion, or hydraulic fracturing. Despite the fact that hydraulic fracturing technology has advancedsignificantly over the past fifty years, our ability to model the process hasnot changed as rapidly. As a matter of fact, this technique has been sosuccessful that in the past, designing the treatment with a high degree ofprecision was not of any interest. ut as the industry moved towardsapplications of very high volume/rate, and highly engineered and sophisticatedhydraulic fracturing treatments, the demand for more rigorous designs in orderto optimize the procedure have become more important. On the other hand, without a thorough understanding of the physical process and the factors thatare involved, our ability for an optimal design is limited. Modelling fluidflow combined with heat transfer in the reservoir has been used by the industryfor a long time, and the fracturing process was often designed based ontwodimensional closed-form solutions, such as Geertsma-deKlerk(3), or GdK in brief, and Perkins-Kern(4) and Nordgren(5), or PKN.

Knowledge of gas saturation history is very important in determining gas recovery from gas reservoirs with water influx. Water imbibition is known to control gas recovery. Spontaneous imbibition experiments have been traditionally employed to determine gas saturation. On-line NMR relaxometry is introduced as a method for monitoring co-current imbibition. A group of plugs from a Western Canadian sandstone reservoir were selected and a series of imbibition tests were run. NMR was used to measure the amount of water imbibed in the cores and the gas saturation during each experiment was, in turn, measured. The values of final residual gas saturation and the production profiles were compared to the results from corresponding counter-current imbibition tests. The correlations of residual gas saturation with initial imbibition rate and other operating parameters were investigated. Through interpretation of the NMR spectra, bound water T2cutoff values were obtained. Water distribution in different pore sizes during the experiments was also calculated. The initial imbibition rate in different pore sizes was measured. Empirical equations from the literature, which were used to describe the behaviour of co-current imbibition tests, were applied to the experimental data. The proposed methodology can be used to evaluate the mechanisms of water imbibition in gas reservoirs. Introduction The understanding of the mechanisms that govern spontaneous water imbibition in gas-water systems is important to the development of natural gas reservoirs. Many researchers indicate that residual gas saturation is affected by factors such as wettability, imbibition rate, initial water saturation, and also the experiment methods(1–3). In this work, a group of sandstone plugs underwent co-current imbibition tests. The fluid saturations were measured using Nuclear Magnetic Resonance (NMR) relaxometry. The results were compared with those coming from counter-current imbibition tests from previous work(4, 5). Some results from the literature(6, 7)were also tested against our experimental results. In 1960, Handy(6) developed an equation to describe the behaviour of co-current imbibition tests. He postulated that the weight or volume of imbibed water is proportional to the square root of imbibition time: Equation (Available In Full Paper) In this equation, A and Nwt are the cross-section area of the core and the volume of water imbibed into the core, respectively. Swf is the water saturation behind the imbibition front. Kw and Pc are the effective water permeability and capillary pressure at Swf, respectively. Finally, Φ?is the porosity and µw is the viscosity of the imbibing brine. Li and Horne(7) point out there are some disadvantages to Handy's equation (6) since effective water saturation behind the front and capillary pressure cannot be calculated separately, and the relationship between the square of weight gain and time is not a straight line during the later period of water imbibition. They developed an equation to describe the relationship between the imbibition rate and gas recovery based on the assumption of a piston-like imbibition flow. In their equation, the imbibition rate should be in a linear relation with the reciprocal of gas recovery.

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