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Analysis Method Theory


Analytical Models (IHS RTA / IHS CBM)

These models are listed in the order that they are described:

Vertical Model — simulates the pressure response in a vertical well within a rectangular-shaped reservoir with homogeneous or dual-porosity characteristics. 

Fracture Model — simulates the pressure response in a vertical well intercepted by an infinite-conductivity vertical fracture within a rectangular-shaped reservoir with homogeneous or dual-porosity characteristics.

Horizontal Model — simulates the pressure response in a horizontal well within a rectangular-shaped reservoir with anisotropic heterogeneities or dual-porosity characteristics.

Multilayer Model — simulates the transient flow in any number of independent layers commingled at the wellbore.

Composite Model — used when reservoir and fluid properties change at some distance from the wellbore.

Water-drive Model — a cylindrical reservoir with a concentrically cylindrical aquifer.

Horizontal Multifrac Composite Model — simulates the pressure response for a non-contributing horizontal well with multiple identical, uniformly distributed fractures. Note that the region between the fracture tips (inner region) may have different permeability then the rest of the reservoir.

Horizontal Multifrac SRV (Uniform Fracs) Model — the same as the horizontal multifrac composite model, but includes only the inner region of the reservoir — not the outer reservoir region.

Horizontal Multifrac Enhanced Fracture Region Model — simulates the pressure response for a non-contributing horizontal well with multiple identical, uniformly distributed fractures. Each fracture is surrounded by the region of higher permeability (enhanced fracture region), while the remaining space between fractures may have lower permeability.

General Horizontal Multifrac Model — simulates the pressure response in a horizontal well intercepted by multiple infinite-conductivity fractures. Fractures have different lengths and can be located anywhere along the horizontal wellbore.

Horizontal Multifrac Repeating Pattern Model — simulates the pressure response in a horizontal well intercepted by multiple infinite-conductivity fractures. The wellbore is located in the center of the reservoir, and fractures are distributed symmetrically within each stage, and all stages are identical.


Decline (IHS DeclinePlus)

Traditional Decline — generates a forecast of future production rates based on historical production data to determine EURClosed Expected Ultimate Recovery.


Flowing Material Balance  (IHS RTA / IHS CBM)

This analysis method uses reservoir performance flow data to evaluate original hydrocarbons in place. This technique is a good alternative to the static material balance method for estimating hydrocarbon in place without having to shut the well in. This method is also applicable to dry, or dewatered CBMClosed coalbed methane reservoirs, where there is only gas (not water) production.




Hybrid Model (Beta) (IHS RTA)

The hybrid model is essentially a numerical model, but with certain modifications to significantly reduce computation time, so that it is almost as fast as an analytical model.


Material Balance (IHS DeclinePlus / IHS CBM)

Gas Material Balance — a performance-based interpretation method used to determine original-fluids-in-place (OFIP) based on production and static pressure data. It relates the original oil, gas, and water in the reservoir to the production volumes and current pressure conditions and fluid properties.

Oil Material Balance — a performance-based method used to interpret, analyze, and model static pressure and production data from oil reservoirs in order to determine pool groupings, original oil in-place (OOIP), gas cap size, drive mechanisms, and theoretical recovery factor.


Numerical (IHS RTA / IHS CBM)

These analysis methods model multiphase flow situations in the reservoir. Numerical models can also be used to enhance the modeling exercise when detailed reservoir data is available in more complicated cases.


Probabilistic & Sensitivity (IHS RTA / IHS CBM)

A probabilistic analysis is a technique to quantify the impact of uncertainties on output variables, and to find the range of probable outcomes as well as the most likely.

A sensitivity analysis is the systematic investigation of the reaction of the simulation outputs to extreme values of the model’s input



Pseudo-steady state (PSS) models simulate CBM vertical reservoirs and hydraulically fractured reservoirs. You can obtain reservoir parameters by history matching to gas rates, water rates, and sandface flowing pressures, and generate two-phase (gas + water) forecasts.


Ratio Analysis (IHS DeclinePlus)

Water-Oil Ratio — a performance-based method of trending future water production for the purpose of forecasting oil production, water production, and determining EUR. WORClosed water-oil ratio forecasting is an empirical analysis method.


Surveillance (IHS DeclinePlus)

This analysis method facilitates understanding of reservoir performance and helps to identify opportunities to improve ultimate recovery.

Hall Plot — enables you to draw conclusions about average injectivity performance.

VRR — aids in identifying parts of a field where increasing or decreasing amounts of water must be injected in order to reach or maintain voidage replacement ratio (VRR) targets.


Typecurve (IHS RTA / IHS CBM)

Agarwal-Gardner — estimates fluids in-place volumes, drainage area, reservoir permeability, skin around the well, or fracture half-length / fracture conductivity for hydraulically fractured wells.

Blasingame — estimates skin, formation permeability, in-place fluid volumes, and reservoir drainage area. Blasingame has several families of advanced type curves, such as finite conductivity, elliptical, water drive, open-hole horizontal well typecurves, in addition to classic radial, and fracture typecurve models.

Compound Linear — well-suited for analyzing horizontal multi-fractured wells drilled in tight gas or shale reservoirs.

Fetkovich — estimates EUR, skin, and formation permeability from the rate history of the well.

NPI — the inverse of the Agarwal-Gardner typecurves is often preferred by those who come from a pressure transient analysis domain. Outputs are as the same as Agarwal Gardner.

Transient — useful for datasets containing long-term transient flow. Outputs are the same as other modern typecurve-match techniques.

Water drive — matches production data to typecurve models characterized by different levels of aquifer mobility, relative to the reservoir. This typecurve model is implemented in Blasingame, Agarwal-Gardner, and normalized pressure integral (NPI).

Wattenbarger — well- suited for reservoirs that exhibit a long-lasting transient linear flow regime. This method is particularly useful for the analysis of tight and shale gas wells.


Unconventional Reservoir (IHS RTA)

This analysis method is used to interpret the linear flow signal exhibited in multiple-stage hydraulically fractured unconventional reservoirs, and to forecast production from such reservoirs.


Volumetrics (IHS DeclinePlus / IHS CBM)

This analysis method is a technique used to estimate the original hydrocarbon fluid volume in a reservoir based on the properties of the reservoir rock along with limited knowledge of the fluid saturations.




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