A polyalcohol/asphalt system developed by Qingdao Millennium Energy Co., Ltd. has been tried to be used in Dongying Shengli Oilfield. The system mixes a kind of polyalcohol with cloud point and deformable asphalt. Relying on the emulsification of polyalcohol, the oxidized asphalt is stably dispersed in the water-based drilling fluid without the addition of surfactants.
The inhibition effect of polyalcohol in mud shale can be summarized into three points:
(1)Reduce activity, stabilize mud shale through osmosis;
(2)Cloud point behavior, blocking mud shale by polyalcohol particles;
(3)Adsorption, polyalcohol can be strongly adsorbed on the surface of mud shale, forming an adsorption layer and preventing shale from dispersing and expanding.
The deformable asphalt can seal the formation pores, micro-cracks and layers, and form a tight hydrophobic film on the well wall to prevent water erosion of the formation and play a role in stabilizing the well wall, while the polyalcohol can form oil droplets at the temperature above the cloud point, providing the system with the corresponding lubricity, so that the system has better lubrication performance and better HTHP FL.
The system has successfully solved the problem of high pressure failure directional well drilling.
For example, when drilling the Shengli 86 well, two high-pressure zones were encountered and the deviation was 46°. The polyalcohol system was used to successfully control the HTHP fluid loss and reduce the torque and tension of the drill string.
Compared with the traditional polymer system, polyacolhol system drilling fluid developed by Qingdao Millennium Energy Co., Ltd. can:
(1) Increse the the drilling speed and reduce the dilution times.
(2) Improve the texture of cuttings.
(3) Enhance the ability to resist gypsum invasion, gas invasion, cement invasion and solid phase invasion.
