Horizontal Well Application In a Vertical Miscible Flood
Authors: Adamache I. , McIntyre F.J. , Pow M. , Lewis D.D. , Davis R. , Butler S. , Kuhme A. , Bloy G. , Van Regan N. , Sheppard G. , Grenon J.P. 
Published: March 2010

This paper describes the planning, drilling and completion of the first horizontal well (16-29-108-8W6M) in a Canadian vertical hydrocarbon miscible flood: Rainbow Keg River, G Pool; this well was also the first medium radius horizontal well drilled by Husky. The success of this well in 1989 encouraged the expansion of horizontal technology in Rainbow. In the G Pool two other horizontal wells were drilled successfully (in 1992 and 1993) to further increase the productivity and oil recovery of this reservoir. Also, based on the successful performance of 16–29, nine other horizontal wells were drilled, one existing horizontal well was extended and also a horizontal well re-entry was put in production successfully, in other Rainbow miscible flood pools.

Management set up a multi-disciplinary task force to determine the optimum application of horizontal well technology and to select the first location. The task force selected Rainbow Keg River G Pool, in which a miscible flood has been in progress since 1972. The horizontal well, 16–29, was subsequently planned, drilled and completed in this pool to increase oil production rate and ultimate recovery-by minimizing gas coning.

To minimize oil sandwich (the oil bank remaining between solvent and water) loss in this vertical miscible flood, the well was to be placed as low as possible with respect to the oil/water contact while avoiding water coning. To improve the interpretation of reservoir characteristics and fluid contacts, a program of well testing and production logging was conducted at offsetting vertical wells, To validate the interpretation and obtain additional reservoir information, a vertical pilot hole was drilled through the productive reef prior to plug-back and kick-off for the horizontal hole.

The surface location was determined based on 3D seismic, which was used to map the Keg River structural surface. A comprehensive formation evaluation program including coring, logging and drill-stem testing was conducted in the vertical pilot hole) which contributed to the successful placement of the horizontal hole. The azimuth of the horizontal' hole was determined from previous information about the direction of natural open fractures.

Initial production and pressure data has confirmed the proper placement of the horizontal hole in the remaining oil sandwich, The productivity index of the horizontal well has been more than three times that of the best vertical well in this pool.

Although the drilling and completion programs were designed to minimize complications which could lead to cost overruns, the actual well cost was 1.7 times the initial estimate and 2.5 times the cost of a conventional vertical well. Cost overruns were due to lost time incidents in the vertical section only. In spite of the cost overruns this horizontal well was successful and paid out capital costs in nine months.

Two more horizontal wells were subsequently drilled in the same pool. Well costs were reduced to less than 1.5 times the cost of a conventional vertical well. Both subsequent wells were also successful in reducing coning and increasing recoverable oil.