Modelling Of Drilling Rate For Canadian Offshore Well Data
Authors: Wee W. , Kalogerakis N. 
Published: March 2010

The Bourgoyne and Young drilling model was applied to data from wells drilled in Canadian offshore areas. Field data was fitted to the model equations to establish a relationship between the penetration rate and eight drilling variables. Several statistical tests and parameters were computed to evaluate the results. Over-all, the departure between actual and predicted responses range from 5% to 15%. Results obtained using the eight parameter Bourgoyne and Young model were shown to be superior to those obtained using a simple three parameter model similar to the R-W-N relationships. Statistical techniques showed that for the data analyzed, the Bourgoyne and Young equation could be reduced to a simpler jive parameter model without a significant loss in predictive capability. Finally, the modelling procedure was applied to combined data from more than one well by expanding the basic model equation to include the effect of factors specified to individual wells.

Scope

Successful modelling of the penetration rate can lead to reduced drilling costs through optimization of the drilling time. Of the numerous expenses associated with drilling operations, it is the daily rig charge which normally accounts for the major portion of total drilling costs. This is particularly true in offshore areas where rig costs may exceed similar charges for land-based operations by 30 to 40 times and can range from $180,000 to $250,000 per day. Offshore rigs may typically spend 55% of the total time on location with the actual drilling function which includes time for making connections and trips. The remaining 45% of rigtime may be spent logging, cementing, formation testing, resolving hole problems or waiting-on-weather. On land, the actual drilling function may account for 60% to 75% of the total location time.

In this paper, the dril1ing model of Bourgoyne and Young(1) is applied to field data from Canadian offshore wells to establish a relationship between the Penetration rate and eight drilling variables. Simulation of the drilling process in a given formation type is accomplished by fitting the proposed model to actual field data through the use of a multiple regression analysis method. Bourgoyne and Young tested their technique in the offshore Louisiana Gulf Coast area and the model has been applied to wells in the Arabian Gulf(2). This paper attempts to verify the Bourgoyne and Young model for two wells drilled in the Canadian offshore. The validity of the results is evaluated using statistical model adequacy tests not discussed in previous publications. Alternative simplified forms of the basic model equation are applied and an extension of the model equations to combined datasets from multiple wells is examined.

Optimization of any process generally requires a thorough understanding of the many factors which affect it. Mathematical models which accurately portray the dril1ing process can greatly facilitate the optimization procedure. At present, such models are still at an early stage of development and cannot be routinely used to design drilling programs. Present day design of drilling programs relies greatly on past experience and proven methods employed in the area.