Well Spacing Calculator

Calculator

Method

Choose how spacing will be determined.

Pattern

Pattern changes area-to-spacing geometry.

Rectangular ratio (Y/X)

1.00 gives a square-equivalent rectangle.

Drainage area per well

Area unit

Total field area

Field area unit

Planned number of wells

Permeability k

Porosity φ

Viscosity μ

Total compressibility c_t

1/psi

Time t

Overlap allowance

Higher overlap reduces spacing to allow interference.

Safety factor

Adds margin to the computed spacing.

Rounding decimals

Controls display precision and exports.

Reset

Example data table

Scenario	Method	Pattern	Key input	Recommended spacing (approx)
Conservative spacing	Drainage area	Square	40 acres per well, 10% safety	~ 424 m (1,390 ft)
Moderate density	Field development	Triangular	640 acres, 16 wells, 5% safety	~ 428 m (1,404 ft)
Early-time interference	Radius of investigation	Rectangular	k=50 mD, φ=0.20, μ=1.2 cP, c_t=1e-5, t=24 hr	Depends on overlap and ratio

Examples are illustrative. Confirm with your reservoir model and constraints.

Formulas used

1) Drainage area geometry

Square pattern: A = S² ⇒ S = √A
Triangular pattern: A = (√3 / 2) · S² ⇒ S = √(2A / √3)
Rectangular pattern: A = Sx · Sy with Sy = R · Sx ⇒ Sx = √(A/R), Sy = R · Sx

2) Field development

Area per well: A = A_field / N, then apply the geometry above.

3) Radius of investigation (transient planning)

r_i(ft) = 0.198 · √( k·t / (φ·μ·c_t) )
Base spacing: S_base = 2·r_i·(1 − overlap)

Safety margin: S = S_base · (1 + safety%).

How to use this calculator

Select a method that matches your planning stage.
Choose a pattern, then enter the required inputs.
Set overlap only for radius-based planning scenarios.
Add a safety factor for uncertainty and constraints.
Click Calculate, then export results as CSV or PDF.

FAQs

1) Which method should I use for early planning?

Start with the drainage area method for quick screening. If you already know the field area and planned well count, the field development method aligns better with layout decisions.

2) Why does the pattern change spacing?

Patterns assign different geometric areas to each well. For the same spacing, a triangular layout covers more area per well than a square layout, so the spacing-to-area relationship changes.

3) What does the rectangular ratio mean?

The ratio is Sy/Sx. Use it when surface corridors, faults, or lease boundaries force anisotropic spacing. A ratio of 2 means wells are twice as far apart in Y as in X.

4) How should I choose the safety factor?

Use a higher safety factor when properties are uncertain, compartmentalization is likely, or surface access is difficult. Keep it small when data quality is high and you will confirm with simulation.

5) What is overlap allowance in the radius method?

Overlap represents intended interference between wells. Increasing overlap reduces spacing so drainage areas overlap more. It can reflect infill development or tighter spacing to accelerate recovery.

6) Can this replace reservoir simulation?

No. This tool provides geometric and transient-based estimates to guide layout. Confirm spacing with simulation, history matching, completions strategy, and operational constraints before committing capital.

7) Why do I see both meters and feet?

Spacing decisions are often discussed in both systems. Showing both reduces conversion mistakes and makes it easier to share outputs across teams and documentation standards.

8) What inputs most strongly affect spacing?

Drainage area (or field area per well) dominates geometric spacing. In the radius method, permeability, time, and compressibility strongly influence the radius estimate, which then drives spacing.