Sometimes, the implementation of contractual obligations is affected by the events that, while reducing productivity, require the contractor to spend unforeseeable costs and use more resources such as manpower, machinery and equipment to achieve, accurate and timely, to the same results as were provided at the time of contract conclusion. Although drilling oil and gas wells is carried out based on a series of studies and predictions included in the contract, the risk of uncertainty is so high that its implementation is sometimes disrupted. Of course,, the "disruption" is a concept that is used initially in construction projects to formally recognize the recovery of the costs imposed on the contractor for the events that cause disruption but it may be implemented in oil and gas well drilling contracts. It is obvious that the drilling contractor's entitlement to receive the fee requires proving the existence of a causal relationship between the cause, the disruption, and the employer.
Keywords: Cardinal Change, Compensable Damage, Disruptive Event, Liability Clause, Productivity, Uncertainty.