Reservoir Net Pay
Compute a reservoir's net pay (net productive thickness) by multiplying the gross interval thickness by the net-to-gross ratio (N/G), the fraction of rock with enough porosity and permeability to produce. Shale layers, tight rock or water zones are discounted. The net pay, not the total thickness, is what enters the oil and gas volume calculations. Enter the gross thickness and the net-to-gross ratio.
Resultado
—
Net pay do reservatório
Nem toda a espessura de um intervalo perfurado produz óleo. O net pay (espessura produtiva líquida) é só a parte da rocha que tem porosidade e permeabilidade suficientes para realmente fluir hidrocarboneto — descontando as intercalações de folhelho (argila impermeável), zonas compactas, e trechos abaixo do contato óleo-água. Calcula-se net pay = espessura bruta × razão net-to-gross (N/G), a fração 'boa' do intervalo. Essa distinção é vital: usar a espessura bruta no cálculo de volumes (OOIP) superestimaria grosseiramente as reservas, contando rocha que não contribui. O net pay é determinado com cortes (cutoffs) de porosidade, saturação e argilosidade aplicados aos perfis do poço — e a definição desses cutoffs é uma das decisões mais consequentes (e debatidas) da avaliação de formações. Informe a espessura bruta e a razão net-to-gross.
Related Tools
Water Saturation (Archie)
Compute a reservoir's water saturation (Sw) by Archie's equation (with a=1, m=2, n=2), Sw = √(Rw/(φ²·Rt)), from the formation-water resistivity (Rw), the rock's true resistivity (Rt) and the porosity (φ). It is the fundamental petrophysics equation: it relates the resistivity measured by electric logs to the fraction of pores filled with water — and, by complement (1−Sw), with hydrocarbons. Enter Rw, Rt and the porosity.
Leverett J-Function
Calculates the Leverett J-function, which normalises capillary pressure by interfacial tension, contact angle and the square root of the permeability-to-porosity ratio. It collapses capillary pressure curves from samples with different properties onto a single rock-type curve. Enter the capillary pressure, interfacial tension, contact angle, permeability in millidarcy and porosity.
Oil Formation Volume Factor (Bo)
Compute the oil formation volume factor (Bo) by dividing the volume the oil occupies at reservoir conditions by the volume it occupies at the surface (stock-tank barrels). Bo is always greater than 1 because, in the reservoir, the oil is hot and has dissolved gas, occupying more space; as it rises and loses gas and heat, it shrinks. It is essential to convert reservoir volumes into surface production. Enter the volumes at reservoir and surface conditions.
Reservoir Recovery Factor
Compute a reservoir's recovery factor, RF = (Np/N)·100%, the fraction of the original oil (N, or OOIP) that will actually be produced (Np). It is one of the most important — and uncertain — numbers in the industry: primary recovery (natural energy) is usually 5–15%; with secondary recovery (water/gas injection) it rises to 30–50%; and advanced methods (EOR) can go further. It defines the field's economic value. Enter the cumulative production and the original oil in place.
Density-Log Porosity
Compute a reservoir rock's porosity from the density log, φ = (ρma − ρb)/(ρma − ρf), where ρma is the matrix (mineral) density, ρb the bulk density read by the log and ρf the pore-fluid density. It is one of the most used petrophysical methods to estimate porosity in wells, since the bulk density drops as the pore volume (filled by less dense fluid) increases. Enter the matrix, bulk (log) and fluid densities.
Oil in Place (OOIP)
Compute a reservoir's original oil in place (OOIP) by the volumetric method, OOIP = 7758·A·h·φ·(1−Sw)/Boi, in stock-tank barrels (STB). It combines the reservoir area (acres), the porous thickness (ft), the porosity (φ), the water saturation (Sw) and the oil formation volume factor (Boi). The constant 7758 converts acre-feet into barrels. It is the basis of any oil-field evaluation. Enter the area, thickness, porosity, water saturation and Boi.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.