Toe-to-Heel Waterflooding
趾端至跟部驱油法进行重力稳定注水开发
Toe-to-heel waterflooding is a gravity stable short-distance displacement process. A vertical injector, perforated at the lower part of the layer, injects water and pushes the oil towards the horizontal producer, placed at the upper part of the layer with the toe towards the vertical injector.
该技术以直井作为注水井,水平井为生产井,采用井位交错排列的线性注水方式.水平井的趾端靠近直井,水平段位于油层上部,直井在油层下部处射孔,形成一种短距离驱油过程.油水重力分异作用使注入水向下流动,而水平井作为接收器引导水向上流动;两种力共同作用的结果是在跟部见水,然后是驱油前缘沿水平井段向前流动,从而使水流波及大部分生产层段.
A very promising technology, lab results have shown incremental oil recovery of up to 31% original oil in place. We are now working with several operators to field test this technology.
Benefits of toe-to-heel waterflooding
Increased ultimate oil recovery
Uses existing vertical wells
Easy control of the operation (water breakthrough always at the tow)
Less sensitive to rock heterogeneity
More possibilities for optimization of design and production operation
Increased water injectivity
TTHw技术的优点
·提高了最终采收率；
·利用了已有的直井；
·施工过程容易控制(水总是在水平井的端部突破)；
·对岩性非均质性不敏感；
· 优化设计和生产的可能性更大；
·提高了注水效率。
Toe-to-heel waterflooding is also best used in the poorest conditions for conventional waterflooding:
Large pay thickness
Upward finning trend (downward permeability increase)
High permeability streak at the bottom of the formation
High density contrast between injected water and produced oil (e.g. high salinity injected water)
Screening Criteria for Toe-to-Heel Waterflooding
Reservoirs suitable for switching to toe-to-heel waterflooding from conventional waterflooding are characterized by:
Pay thickness > 10m
Horizontal permeability > 200 mD
Oil saturation > 50%
Large well spacing
Intensive water tonguing at the bottom of later due to either a thief zone or under-riding
TTHw技术的适用条件
老油田从常规水驱转到TTHw技术的适用条件
·产层厚度大于10m；
·水平渗透率大于200 mD；
·原油饱和度大于50％ ，
·井距大；
·产层下部由于高渗透层等缘故存在强烈的水舌进。
New reservoirs suitable for toe-to-heel waterflooding are characterized by:
No gas cap
Pay thickness > 6m
Oil viscosity < 2,000 mPas
Horizontal permeability > 200 mD
Oil density < 980 kg/m3
Oil saturation > 50%
Equivalence
One dual lateral horizontal well replaces four vertical producers when replacing the 9-sport pattern application
One horizontal well can replace two vertical producers when replacing the 5-spot pattern application
新油田TTHw 技术的适用条件
·无气顶；
·储层厚度大于6m；
·原油粘度小于2000 mPas
·水平渗透率大于200 mD；
·垂直渗透率大于100 mD；
·原油密度小于980 kg／m3；
·原油饱和度大于50％。
Toe-to-heel oil recovery process专利：
http://www.freepatentsonline.com/6167966.html
