CBM Multilateral Drainage & Lateral Spacing Calculator

Model complex fishbone (pinnate) horizontal well drainage envelopes, calculate Joshi effective wellbore radius (r_w'), and optimize lateral inter-branch spacing.

Lateral Architecture & Coal Properties

Main Trunk Lateral Length L (ft):

Number of Fishbone Rib Branches: Opposed bilateral sidetracks

Average Rib Branch Length (ft):

Seam Permeability Anisotropy (k_x / k_y): Face cleat k_x vs Butt cleat k_y

Face Cleat Permeability k_x (mD):

Net Coal Seam Thickness h (ft):

Drainage Envelope & Equivalent Skin

Total Well Contact Length:

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Stimulated Drainage Area:

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Apparent Wellbore Radius r_w':

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Equivalent Geometric Skin S_mult:

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Productivity Index Boost Factor:

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Inter-Rib Interference Check:

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Frequently Asked Questions

Why drill multilaterals instead of hydraulically fracturing vertical CBM wells?

In friable, shallow, or gassy coals, hydraulic fracturing can crush the coal into fine powder, embed proppant, or accidentally fracture into bounding water-bearing sandstones. Multilateral drilling provides massive in-seam contact without pumping proppant or risking water breakthrough.

What is the main operational challenge of horizontal CBM wells?

Coal stability and fines production. Low-strength coals can collapse around the openhole lateral during dewatering depressurization. Many operators install slotted liners or pre-perforated casing in the main trunk.