A verbal agreement or a handshake is not a foundation on which to build a major borehole drilling project. The contract between the client and the drilling contractor is the legal framework that defines responsibilities, allocates risk, establishes quality standards, and provides remedies when things go wrong. A well-drafted drilling contract, supported by a clear bill of quantities, is as important to a successful project as a good geological survey.
Purpose of the Drilling Contract
The drilling contract achieves several critical functions:
- It defines precisely what work is to be done, to what standard, and within what timeframe.
- It establishes the price and payment terms.
- It allocates the risks inherent in subsurface work between client and contractor.
- It sets out the consequences of non-performance.
- It provides mechanisms for resolving disputes without litigation.
Without a contract, the client has limited legal recourse if the contractor underperforms, and the contractor has no protection against scope creep or non-payment. Both parties benefit from a clear, fair, and enforceable agreement.
Key Contract Components
1. Scope of Work
The scope must be unambiguous. It should specify:
- The number of boreholes to be drilled.
- Target depth or depth range.
- Borehole diameter at each stage.
- Drilling method to be used.
- Casing and screen specifications: material, diameter, wall thickness, slot size.
- Gravel pack specification: material, gradation, and placement method.
- Grouting requirements: depth, material, and installation method.
- Wellhead construction standards.
- Development method and minimum duration.
- Pumping test requirements: type, duration, and reporting.
- Water quality sampling and laboratory analysis.
- Completion documentation: drilling log, pumping test report, and completion certificate.
Any ambiguity in the scope invites dispute. If a specification is important enough to affect quality, it belongs in the contract.
2. Contract Price and Payment Terms
Borehole drilling contracts are typically structured on one of two bases:
Unit Rate (Remeasurement) Contract: The client pays for the actual quantities of work completed, based on agreed unit rates in the bill of quantities. The contractor is paid per metre drilled, per metre of casing installed, and so on. This structure is most common in borehole contracts because it allocates geological depth uncertainty fairly — the client pays for the depth actually needed, not a fixed price for a depth estimate. Risk of geological variation is shared.
Lump Sum Contract: The contractor agrees to complete all specified work for a fixed total price, regardless of the quantities of materials or time required. This transfers more risk to the contractor but typically at the cost of a higher price premium. It suits well-defined projects in areas of known, predictable geology.
Day Rate Contract: The client pays for the contractor’s time and equipment at an agreed daily rate, plus materials at cost plus a defined margin. This is the highest-risk arrangement for the client from a cost certainty perspective, but may be appropriate for exploratory drilling in complex geology.
Payment schedules typically link payments to milestone completion: mobilisation payment on arrival on site, interim payments as drilling progresses, and a final payment on completion and acceptance of the borehole.
3. Technical Specifications
All materials and methods must be specified in detail, either within the contract body or by reference to recognised standards (national drilling standards, British Standards, ISO standards, or equivalent). Specifications should address:
- Minimum casing wall thickness and yield strength.
- Thread type and joint sealing requirements.
- Screen open area percentage and slot tolerances.
- Gravel pack grain size gradation and cleanliness.
- Grouting mix proportions and minimum set strength.
- Pumping test procedures (reference to standard methods).
- Water quality analysis parameters and accredited laboratory requirements.
4. Programme and Milestones
The contract should include a drilling programme with defined milestones: mobilisation date, drilling completion date, development and testing completion date, and documentation submission deadline. The consequences of delay (liquidated damages, extension of time clauses, force majeure provisions) should be clearly stated.
5. Supervision and Reporting
The contract should require the contractor to submit daily drilling reports, which are the primary means of supervising ongoing work. Reports should record depth drilled, formation encountered, casing installed, fluid consumption, water strikes, and any operational issues. These reports are the client’s record of what occurred underground.
6. Defects Liability
A defects liability period — typically 6–12 months after completion — during which the contractor is responsible for rectifying defects in materials or workmanship at no additional cost. This provides protection against latent defects that only become apparent after commissioning.
The Bill of Quantities
The bill of quantities (BOQ) is both a pricing document and a measurement document. It lists every item of work and supply in discrete, measurable units. During tender, each contractor inserts their unit rates; during construction, quantities are measured and valued using those agreed rates.
A well-structured BOQ prevents disputes about what is included in the price and provides a transparent mechanism for valuing variations to the original scope.
Dispute Resolution
No contract is complete without a dispute resolution mechanism. Standard approaches include:
- Amicable negotiation — first step for all disputes.
- Expert determination — referral to an independent technical expert for issues of a technical nature.
- Arbitration — binding resolution outside the court system, often faster and less expensive than litigation.
- Court proceedings — final resort, generally to be avoided given the time and cost involved.
The governing law and jurisdiction of the contract should be explicitly stated.
