It is an important concern to prevent asphaltene related damages in hydrocarbon reservoirs.There are many investigations about asphaltene and its effects and how to reduce them during the oil production. In the present work, some experiments have been conducted to investigate the effect of the SiO2, NiO, and Fe3O4 nanoparticles on the oil recovery, and find out how they adsorb asphaltene and prevent its precipitation. Moreover, instead of crude oil, a synthetic solution with a given component concentration is used. Results of this study show that in solutions without nanoparticles, increase in the amount of normal heptane causes more asphaltene aggregation takes place; however, in the presence of nanoparticles, increasing the normal heptane would result in an increase in the asphaltene adsorption on the surface of nanoparticles. Furthermore, It is shown that the amount of oil recovery in the presence of different nanoparticles corresponds to the ordering: SiO2> NiO> Fe3O4.

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Fracture ballooning usually occurs in naturally fractured reservoirs and is often mistakenly regarded as an influx of formation fluid, which may lead to misdiagnosed results in costly operations. In order to treat this phenomenon and to distinguish it from conventional losses or kicks, several mechanisms and models have been developed. Among these mechanisms under which borehole ballooning in naturally fractured reservoirs take place, opening/closing of natural fractures plays a dominant role. In this study a mathematical model is developed for mud invasion through an arbitrarily inclined, deformable, rectangular fracture with a limited extension. A governing equation is derived based on equations of change and lubrication approximation theory (Reynolds's Equation). The equation is then solved numerically using finite difference method.Considering an exponential pressure-aperture deformation law and a yield-power-law fluid rheology has made this model more general and much closer to the reality than the previous ones. Describing fluid rheology with yield-power-law model makes the governing equation a versatile model because it includes various types of drilling mud rheology, i.e., Newtonian fluids, Bingham-plastic fluids, power-law, and yield-power-law rheological models. Sensitivity analysis on some parameters related to the physical properties of the fracture shows how fracture extension, aspect ratio and length, and location of wellbore can influence fracture ballooning. The proposed model can also be useful for minimizing the amount of mud loss by understanding the effect of fracture mechanical parameters on the ballooning, and for predicting rate of mud loss at different formation pressures.

The total of the gas in shale gas reservoirs is sourced from a combination of free, adsorbed and dissolved/diffused gas. The mechanisms of production of free and adsorbed gas have been studied by numerous researchers. In contrast, the evolution of the dissolved gas and its contribution to the total gas production is not well understood. In this study we model the effect of pore micro-structure in organic matter (OM) on the rate of gas production in shale reservoirs. In this regard, first, we solve the gas-in-solid diffusion equation over a general doubly connected spatial domain with external Neumann and internal Dirichlet boundary conditions. The obtained solution is applied systematically to multi-pore porous OM domains and then the effect of pore morphology on the rate of gas production is studied. Our model results show that pore geometry has a slight effect on the gas diffusion process, while total organic carbon, and OM porosity, pore size distribution and specific surface area, are dominant parameters. An abundance of very small pores in OM tremendously increases the diffuse gas contribution in the total gas reserve and production.

To estimate the maximum attainable reach for a horizontal wellbore one needs to investigate the rivalry between the amount of available driving force and the opposing frictional forces. As we provide more driving force through further slack-off, we are more likely to buckle the string and create large normal contact forces, which result in additional tangential frictional forces opposing the forward motion of the BHA. In other words, all the provided driving force will not be transmitted to the desired point (i.e. drillbit) along the string. The greater the stiffness of the drillpipe, the later it buckles and comes into contact with the wellbore wall to create additional normal forces. However, greater stiffness might come with greater weight, as is the case for Steel Drillpipe (SDP) compared to Titanium Drillpipe (TDP), Aluminum Drillpipe (ADP) and Composite Drillpipe (CDP).In this study a new approach for modeling the coupling between tangential frictional force and normal contact force between wellbore and helically-buckled drillstring is developed. The validity of the model is confirmed with experimental data available in the literature. The axial force transfer capability of drillstrings made of SDP, TDP, ADP and CDP are compared. For a limited amount of compressive force provided at the beginning of the horizontal section, different categories of pipes (in the horizontal section of the well) take on different configurations. In addition, along a drillstring some parts remain straight, while some parts buckle helically or sinusoidally. This makes different drillstrings transfer the same amount of provided load differently. In practice, we are able to supply a limited amount of compressive load close to the critical lock-up load in the vertical/slant section of the wellbore. Moreover, below a minimum weight on bit (WOB) drilling becomes impractical. After simultaneous consideration of different buckling modes along the entire drillstring, it is quantitatively shown under what condition ADP can be considered as a superior option over CDP to be used in the horizontal section; and why ADP and CDP have shown a remarkable increase (almost two to three times larger) in the attainable horizontal reach compared to TDP and SDP. This article helps drilling engineers to design an optimum hybrid drillstring for ultra-extended-reach-wells.