INTRODUCTION. 

ECLIPSE is a fully-implicit, three dimensional, general purpose black oil simulator with gas condensate options. The program is written in FORTRAN77 and operates on any computer with an ANSI standard FORTRAN77 compiler and either virtual storage or sufficient real storage. Suitable computers include SUN SPARC station, IBM RS/6000, Silicon Graphics, and Pentium (or better) PCs with more than 24 MB of RAM.

ECLIPSE can be used to simulate 1, 2 or 3 phase systems. Two phase options (oil/water, oil/gas, gas/water) are solved as two component systems saving both computer storage and computer time. In addition to gas dissolving in oil (variable bubble point pressure or gas/oil ratio).

Geometry options.

Both corner-point and conventional block-centre geometry options are available in ECLIPSE. Radial and Cartesian block-centre options are available in 1, 2, or 3 dimensions. The ECLIPSE corner-point geometry option is unique and allows extremely complex geometries to be constructed to give a faithful representation of the reservoir geology. The FILL or GRID can be used to prepare corner-point data for ECLIPSE.²

Fully implicit technology:

ECLIPSE uses the fully-implicit method to provide stability over long time steps. Care is taken to ensure that the non linear fully-implicit equations are solved precisely by reducing all residuals to very fine tolerances. Material balance errors (residual sums) are extremely small. Newton's method are used to solve the non-linear equations.

Although the fully Implicit method is the standard solution procedure used by ECLIPSE it sometimes advantageous to use the IMPES (Implicit Pressure Explicit Saturation) method. IMPES is potentially unstable and should only used on studies with regular grid systems and small time steps.

Dual porosity, PVT & rock data.

The ECLIPSE dual porosity/permeability option is suitable for simulating highly fractured reservoirs. Each grid block is represented by matrix cell and a fracture cell. The Dual Porosity option can also model the effects of gravity imbibition/drainage, molecular diffusion between the matrix and fracture cells, and the viscous displacement of fluid to and from the matrix.

Different table numbers can be used for different parts of the reservoir. Thus, for example, separate saturation tables can be entered for each type of rock.

Miscibility.

ECLIPSE has a three-component miscible flood model. This is intended for the simulation of miscible gas injection processes. The reservoir oil and solvent gas components are assumed to be miscible in all proportions.

Well controls.

The producers can operate at a specified value of the oil rate, liquid rate, gas rate, reservoir fluid voidage rate, bottom hole and tubing head pressure. The engineer supplies a target value for one of these quantities, and limiting values for any of the remaining quantities. If a limit is going to be violated, the well will automatically change its mode of control to keep operating within its allowed limits. A injection well have the similar set of controls.

The simulator contains facilities to control the collective behaviour of groups of wells, or a field as a whole. With guide rate control, the group's target rate is apportioned between all its producers in proportion to either their production potentials or specified 'guide rates', but insuring that no well violates its individual flow rate or pressure limits.

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