No abstract

No abstract

High accurate reservoir simulation is required to better describe multiphase fluids flow to hydraulic fractured wells and improve the development of gas-condensate field. In recent years, numerous research efforts were focused on the developing efficient numerical scheme for full-field simulation and have been facing the problem of tremendous computational resources used to simulate realistic hydraulic fracture details for better and more reliable production optimization. Most of the existent numerical models are based on 3D computational grid that is used for the whole reservoir with grid refining in fracture domain and couldn't completely account all phenomenon within reasonable computational time. New approach for simulation of multiphase multicomponent steady state flow around the hydraulic fractured well is proposed. The approach is based on the splitting the thermodynamic and hydrodynamic problems of multiphase and multicomponent fluids flow. It is also assumed that conductive fracture could be described by 2D surface in 3D permeable formation. Additional coordinate system inside fracture allows to simulate the heterogeneous internal structure of fracture and account the details of the exchange process between fracture and reservoir. Relative permeability and non-Darcy effects in fracture and formation and non-uniform fracture conductivity could be taken account as well. Proposed model can be used for simulation of the steady-state multiphase multicomponent flow to hydraulic fracture of any arbitrary shape. Excellent agreement with commercial dynamic simulators was achieved for gas condensate flows simulation. Significant decrease in computational time in comparison with the existent simulators had been achieved. Introduction Hydraulic fracturing has been proven to be one of the most effective methods for improvement of well deliverability in gas condensate formation. Carlson and Maer1 and Settari et. al2 showed that loss in well productivity due to condensation can be lessened by fracturing the well. Additional advantage of hydraulic fracturing in gas condensate reservoir is reduction of the pressure drawdown that leads to less liquid drop-out. The pressure and flow rate behavior of gas condensate is extremely different from the behavior of a two-phase gas or oil reservoir. A number of published papers have documented the peculiarities of gas condensate mixtures inflow to well: condensate bank accumulation because of condensate drop-out, stripping and non-Darcy effects and etc which can't be described on the basis of so called "black oil" technique. So the multicomponent multiphase fluid model is necessary to predict the performance of hydraulically fractured well in gas condensate formations. The different approaches are being used for gas condensate flow to fractured wells. The most popular of them is based on the multicomponent flow simulation that is done using single computational grid for the reservoir and the fracture. For detailed description of the flow within fracture computational grid is refined around and within fracture using some special techniques for proper grid construction. Such approach was used in papers2,3–6 and allowed to account of various phenomenon taking place under gas condensate flow in vicinity of the hydraulically fractured well. Nevertheless this approach has some certain disadvantages and first of all: large amount of the grid cells and excessive requirements to the computational resources as sequence, difficulties with grid generation around fracture (especially for complex shape fracture), problems with account of vertical heterogeneity of fracture and others. The other approach is to build simplified model of gas condensate inflow to fractured wells. For example the linear model was developed to study of condensate damage at the face of hydraulic fracture by R.R. Ravari et al 7–8. This model was analogous to linear flow toward an infinite conductivity fracture propagating to entire extent of rectangular section of reservoir. Wang et al9 and Indriati10 presented an optimization method for fractures in gas condensate reservoirs, taking into account the relative permeability-to-gas reduction, using an analogy to fracture face damage as presented by Cinco-Ley and co-workers11. The main disadvantage of such models is they can be used only for rough estimation of fractured well productivity in gas condensate formations.

The Yamal region of Western Siberia holds enormous reserves of gas and condensate across many geologic layers including the Achimov deposits of the Late Jurassic and Early Cretaceous. The Achimov however, is among the most challenging layers in the Yamal area with deep bedding, very low permeability, thin laminations and abnormally high reservoir pressures that all greatly complicate the appraisal and production of hydrocarbons. In this regard, accurate formation evaluation is essential to ensure efficient and economically reasonable methods of production. Modern methods of openhole logging, including NMR, acoustic and wireline formation testers (WFT) provide advanced information about the formation and can aid in the most efficient development. In this article we present the results of advanced methods of openhole logging that provides greater understanding of the characteristics of the Achimov reservoir. Special NMR measurements were used to estimate the residual fluid saturation which was confirmed with WFT tools designed for downhole fluid analysis and sampling. We also show how to overcome the negative impact of supercharging on measurements of formation pressure in the Achimov formations and the necessity of carrying out such measurements to validate the hydrodynamic reservoir model. To understand the validity of the samples acquired downhole a simulation was carried out further showing the range of possible variations of the basic PVT properties of hydrocarbons during the sampling. The results of advanced acoustic logging allows to estimate the anisotropy of the mechanical properties of the Achimov layers. The use of the data allowed us to model the fractures resulting from hydraulic stimulation and showed significant differences in the geometric characteristics of the fracture between wells and explains why the lower section of the Achimov are often depleted with respect to the upper sections.

Simulation of sub-and supersonic thermochemical equilibrium flows in plasmatrons is considered. A physicochemical model, numerical method, and computation results for equilibrium inductive coupled plasma flows in a plasmatron are given. An effective preconditioning technique along with an implicit total-variation-diminishing scheme is used to solve the Navier-Stokes equations in both subsonic and supersonic regimes. The governing equations include source terms corresponding to the electromagnetic field influence: the Lorentz force components (so-called magnetic pressure) and Joule heat production. The necessary transport coefficients were calculated in advance for equilibrium air plasma as the functions of pressure and temperature. Transport properties were calculated by the precise formulas of the Chapman-Enskog method in the temperature range 300 < -T < -15,000 K. = Mach number n = external normal vector to a cell face n x , n y = axial and radial components of a vector n P 0 = pressure at an inlet slot, hPa