A Study On Water Crest Characteristics For Finite Conductivity Horizontal Wells In Bottom Water Reservoirs

This study investigated the water flooding behavior of horizontal wells in different situationsin bottom water reservoir. It concluded how to control the water cresting effectively underrational productivity. The conclusions can help to confirm optimal producing rate, delaybreakthrough time of bottom water and enhance the recovery ratio. Meanwhile, this papergave advices to evaluate the well construction andproducing rate of horizontal wells. Thestudy is meaningful to oil fields which have bottom water.This paper focused on fluids flow in three-dimensional permeation media and deducing theproductivity computing model on the base of wellbore hydraulic effect，then gave the solutionof the model. Besides, it established the analytical streamline simulation method of bottomwater reservoir. A process that can determine the breakthrough time of water cresting is given.Furthermore, the study shows how to calculate the saturation of water in water crestingaccording to Buckley-Leverett equation, which can determine the saturation in any positionin any point-in-time of non-piston like displacement. Finally, the author programmedsoftware with VB to solve the issues, and got the following conclusions:1) The pressure drop along the wellbore can not be ignored which means horizontalwells have finite conductivity. The distribution of influx along the wellbore is anasymmetric“U” shape. The nonuniform influx causes different flow patterns in wellbore.2) Breakthrough time varies inversly with gradient of potence which is a function ofwellbore position, influx distribution, and horizontal well length. Therefore, the effect of flowrate on breakthrough time is not a simple proportionate relationship.3) Uplift speed of water cresting is associated with wellbore position, wellbore length,flow rate and position along wellbore. Uplift speed in longitudinal profile increases obviouslywhen height rises.4) Segments in different position have different critical production. Critical productionrelate to vertical height from original contact face, wellbore length. Adopting rationalproduction system could make water cresting stable.5) Shorter the horizontal well is, bigger the uplift height difference of water cresting is.This difference would accumulate as producing time goes on. Longer the horizontal well is,more gentle uplift height difference of water cresting is. But the crest is no longersymmetrical by the effection of prodcution and gradient of potence. 6) Water saturation is reducing from bottom to water flood front of crest.Longitudinally, the increasing interval of same value is smaller and smaller from bottom totop. This phenomenon is more and more obvious. It also proves that uplift speed inlongitudinal profile increases when height rises.