Acid volume for a near-wellbore treatment
Volume of acid to fill the pores and dissolve the carbonate minerals in a ring around the well out to a given radius: in total and per metre of pay. The typical case is the hydrochloric acid preflush ahead of a mud acid treatment of a sandstone.
V = π · (r_s² − r_w²) · h · (φ + (1 − φ) · x_c / X)V_p = π · (r_s² − r_w²) · h · φUniform dissolution in a sandstone: the acid fills the pores and is fully spent on the carbonates of the zone. In carbonate reservoirs the acid dissolves the rock itself and forms wormholes, so the volume there is set per metre of pay, not by this formula. The volume of the wellbore and tubing down to the interval is not included.
Source: Economides, Hill, Ehlig-Economides, Petroleum Production Systems (1994): HCl preflush volume
Inputs
You can change a field's unit: the value is converted to the formula's units automatically.
From the well axis; damage usually lies within 0.3–1 m (1–3 ft) of the wall.
Volume fraction of calcite and dolomite in the solids; 0 counts only the pore volume.
Unit converter for this formulaLength · Liquid volume · Volume per length (capacity) · Fraction and percent
- m1
- cm100
- mm1,000
- km0.001
- ft3.28084
- in39.3701
- 1/32 in1,259.84
- 1/64 in2,519.69
- mile0.000621371
- V/h — Volume per metre of pay–
- V_p — Pore volume of the zone–
- V_m — Acid spent on the carbonates–
More in Fracturing and acidizing
Formation fracture pressure by Eaton's method: the minimum horizontal stress from the overburden and pore pressures through Poisson's ratio. The gradient is given in kPa/m or as an equivalent density.
Expected surface pressure while pumping: the bottomhole treating pressure minus the hydrostatic head plus the friction in the pipe and through the perforations, and the hydraulic power of the pump fleet.
Pressure drop across the perforations: for limited-entry fracturing and for estimating the number of open perforations from a step-down test.
Proppant mass and slurry volume and density for a frac stage from the clean fluid volume and the proppant concentration in kilograms per cubic metre of fluid (in ppa, pounds added per gallon).
Dimensionless fracture conductivity F_CD, the equivalent skin and effective wellbore radius after fracturing from the Cinco-Ley and Samaniego chart, and the fold increase in productivity in pseudo-steady-state flow.
How much calcite or dolomite a cubic metre of acid dissolves: the gravimetric (β) and volumetric (X) dissolving power from the reaction stoichiometry, the mass of rock dissolved and the CO₂ released.
Results are engineering estimates from standard formulas; for design decisions check them against the codes, project documents and specialists' calculations. The formulas carried over from the original set are unchanged, and their errors are described in the notes.