More than 500 horizontal wells have been drilled in Western Canada during the period January 1988 to July 1992. The number of wells drilled each year has increased exponentially. Production data from these wells is providing useful information which could be used to evaluate the performance of these wells.
In this paper, we review a cross-section of the more successful wells and the not-so successful wells. We examine the more important parameters responsible for the performance. Some of these parameters are (1) Reservoir Permeability; (2) Length of the Horizontal Lateral; (3) Drainage Area; (4) Fluid Viscosity; (5) Drive Mechanism; (6) Orientation of the Horizontal Well and (7) Formation Damage from drilling. Based on the performance we attempt to develop screening criteria for wells in the various areas.
Finally, we look at some of the recent innovations. In particular longer horizontal laterals (greater than 1000 meters) underbalanced drilling and re-entries; and the impact they are having on horizontal drilling.
The horizontal drilling activity in Western Canada is impressive, from less than 30 wells in 1988 to 741 wells by the end of 1992. The cumulative production to date from horizontal wells is approximately 5.4 million cubic metres (34 million barrels) In 1992, the production rate was 7,600 cubic metres per day (48,000 Bbls/day).
What have we learned from our half-billion-dollar field experiment? What is Western Canada's real resource base for Horizontal Well Technology (HWT)? Over the next ten to fifteen years can we expect 10,000 horizontal wells to be drilled, enhancing Western Canada's ultimate recovery factor by 2% from about 28% to 30% and thus producing an incremental 300 million cubic metres.
This paper reviews a cross-section of the wells drilled to date in Western Canada and examine some factors that contribute to their success or failure. A detailed review of technical papers and discussions by the operators on the different projects was conducted. These included, presentations at CIM Conferences, Horizontal Well Special Interest Group seminars and monthly meetings, and other local meetings and seminars.
A questionnaire was sent to operators most active in horizontal drilling requesting various field and production data. Responses to the questionnaire in conjunction with production data from individual wells and our technical review provided the basis for our discussions and conclusions. In addition, an attempt was made to provide some general "screening criteria" for horizontal wells in the various areas.
The primary advantage of a horizontal well over a vertical well is the increased contact with the pay zone. Instead of a few metres of the wellbore being in contact with the formation, a horizontal well can have several hundred meters of net pay and a correspondingly higher production rate. Other reasons for drilling horizontal wells are to reduce coning and help produce low permeability reservoirs. Another Important and topical question is, do horizontal wells actually increase the ultimate reserves? How are these concepts standing up to field application? We will discuss these concerns mainly from the Western Canadian Basin perspective.