Recent advances in horizontal drilling and completion technology have
led to the successful completion of multilateral horizontal wells (wel
ls with two or more laterals penetrating separate zones that produce t
hrough a single wellbore to the surface). Evaluating performance of th
ese commingled horizontal wells poses unique problems that have led to
development of a practical procedure for that purpose. This paper dem
onstrates a practical procedure used in evaluating the performance of
three lateral (trilateral) horizontal wells. The procedure, coupling t
he analysis of pressure-buildup and rate/time data, involves use of a
consistent mathematical model to generate pressure and rate responses
for pressure-test interpretation and performance prediction. The proce
dure is demonstrated for several new trilateral wells drilled in the D
os Cuadras field, offshore California. Results from field tests indica
te that the procedure is efficient in evaluating the performance of th
ese wells. Reservoir and well parameters are obtained and the contribu
tion of all laterals is confirmed from pressure-test interpretation. T
he computed model parameters are then used in a rate history match and
accurate longterm performance predictions are made. Deconvolution is
shown to improve the history-match process. In addition, the performan
ce evaluation of these trilateral wells is compared with previously dr
illed single-lateral horizontal wells in the same field. The compariso
n confirms that the new trilateral horizontal well technology is econo
mically viable, allowing reserves to be developed for approximately tw
o-thirds the cost of three single-lateral horizontal wells.