Current industry experience indicates a trend towards the increasing utilisation of multiwell platform programs. Factors such as logistically remote areas of exploration and production, hostile environments, deeper offshore drilling water and deeper production zones are apparently contributing to this increase. Associated with the increasing complexity of such multiwell platform drilling operations, there will be an increase in the need to be aware at the platform of the status of all well bore paths both planned, drilled and in the process of being drilled for paths both planned, drilled and in the process of being drilled for reasons both operational and safety. The use of an onsite mini-computer system specifically programmed for this task and capable of rapid and accurate analysis and suitable output of all stages of the fields drilling life from initial planning to completion, will provide the opportunity for rapid and accurate onsite directional drilling decision making. Appropriate savings in the field's drilling time and development and accurate knowledge of the critical nature of any field drilling situation should be realised. The immediate need to resort to onshore processing facilities with associated delay will be minimised. This paper describes such a system, field tested and proven in the North Sea on multiple-well, twin drilling rig, production platforms. Examples of the analysis capabilities of such a system through the life of a field's drilling program are presented. program are presented


The presence of computer facilities at the drilling site for the analysis of directional survey data in a multi-well environment is a major benefit to help minimize the cost of drilling from a multi-well platform while maximizing the safety of that drilling operation. The features of such a system are the subject of this paper. Although for convenience this paper directs itself to the offshore situation, many of the factors highlighted are also desirable in an onshore situation.

When operating in a multi-well environment, it is vital to closely control the path of each wellbore and to detect potential wellbore intersections, both at the planning stage and when drilling the wells. For reasons of equipment costs and installation logistics, it is common practice that the computer hardware and programs for doing deviation analysis in a multi-well environment reside at a centralized onshore facility. These programs aid the engineers and geologists in formulating their plans for optimal production recovery from the field platforms. Preliminary directional analysis of a well as it is being drilled is normally done at the drillsite by hand or by using simple calculators. Detailed analysis and comparison with other wellbores - planned or drilled - waits until the data can be transmitted to the central facility, scheduled, processed, and the results returned to the drilling crew. processed, and the results returned to the drilling crew. Alternatively. if at all possible, the analysis performed at the wellsite is extended into more detail. With the limited tools available this practice is time consuming and subject to error. In cases where a large number of deviated wellbores have been scheduled from a platform. these delays are longer and often result in additional accrued expense to the drilling operation through rig downtime. In a few cases when an accurate analysis has not been performed or received in time, ensuing hole problems have occurred in which the individual well affects the total plans for the platform. Catastrophic situations-such as intersecting a producing well-are not unknown.

The portability and processing power of present-day minicomputers now provide for installing a computing system at the wellsite and bringing the analysis function to the place where it is most needed. These systems can be programmed to perform accurate directional survey analysis programmed to perform accurate directional survey analysis for a wellbore. project its future path and determine its relationship with the total wellbore plan of the platform. Exploration Logging's Directional Survey Analysis (DSA) and Field Survey Analysis (FSA) programs are a prime example of this capability. These programs operate on the standard minicomputers in the GEMDAS unit and have been field tested and proven in the North Sea on multi-well, twin drilling rig, production platforms.

This paper discusses the features of the DSA and FSA programs and presents examples of the analyses and outputs programs and presents examples of the analyses and outputs required at the wellsite to support a multi-well drilling operation.

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