HORIZONTAL WELL APPLICATION IN A VERTICAL MISCIBLE FLOOD

This paper describes the planning, drilling and completion of the firs t horizontal well (16-29-108-8W6M) in a Canadian vertical hydrocarbon miscible flood: Rainbow Keg River, G Pool; this well was also the firs t medium radius horizontal well drilled by Husky. The success of this well in 1989 encouraged the expansion of horizontal technology in Rain bow. In the G Pool two other horizontal wells were drilled successfull y (in 1992 and 1993) to further increase the productivity and oil reco very of this reservoir. Also, based on the successful performance of 1 6-29, nine other horizontal wells were drilled, one existing horizonta l well was extended and also a horizontal well re-entry was put in pro duction successfully, in other Rainbow miscible flood pools. Managemen t set up a multi-disciplinary task force to determine the optimum appl ication of horizontal well technology and to select the first location . The task force selected Rainbow Keg River G Pool, in which a miscibl e flood has been in progress since 1972. The horizontal well, 16-29, w as subsequently planned, drilled and completed in this pool to increas e oil production rate and ultimate recovery by minimizing gas coning. To minimize oil sandwich (the oil bank remaining between solvent and w ater) loss in this vertical miscible flood, the well was to be placed as low as possible with respect to the oil/water contact while avoidin g water coning. To improve the interpretation of reservoir characteris tics and fluid contacts, a program of well testing and production logg ing was conducted at offsetting vertical wells. To validate the interp retation and obtain additional reservoir information, a vertical pilot hole was drilled through the productive reef prior to plug-back and k ick-off for the horizontal hole. The surface location was determined b ased on 3D seismic, which was used to map the Keg River structural sur face. A comprehensive formation evaluation program including coring, l ogging 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 info rmation about the direction of natural open fractures. Initial product ion and pressure data has confirmed the proper placement of the horizo ntal hole in the remaining oil sandwich. The productivity index of the horizontal well has been more than three times that of the best verti cal well in this pool. Although the drilling and completion programs w ere designed to minimize complications which could lead to cost overru ns, the actual well cost was 1.7 times the initial estimate and 2.5 ti mes the cost of a conventional vertical well. Cost overruns were due t o lost time incidents in the vertical section only. In spite of the co st overruns this horizontal well was successful and paid out capital c osts in nine months. Two more horizontal wells were subsequently drill ed in the same pool. Well costs were reduced to less than 1.5 times th e cost of a conventional vertical well. Both subsequent wells were als o successful in reducing coning and increasing recoverable oil.