Salt-tolerant highly-inhibitive foaming agent for foam drilling of shale formation

Abstract

The invention belongs to the field of surfactants and particularly relates to a highly-inhibitive foaming agent for foam drilling of shale formation and a preparation method of the foaming agent. The foaming agent which is a surfactant is structurally characterized in that a quaternary ammonium salt and polyoxyalkyl ether structure in strong electric charge interaction with shale is introduced while an appropriate hydrophobic carbon chain length is kept. The preparation method includes that alkyl polyoxyalkyl ether dimethyl tertiary amine and methane chloride are subjected to quaternary amination to obtain a surfactant sample. When the foaming agent is applied to the shale formation, remarkable inhibition performance and salt tolerance are provided wile great foaming performance is guaranteed.

Description

technical field [0001] The invention relates to a chemical auxiliary agent for well drilling, in particular to a salt-resistant and strong-inhibiting foaming agent for foam drilling in shale formations. Background technique [0002] Air foam drilling is one of the main methods of underbalanced drilling. Compared with conventional mud drilling fluid, the density of foam fluid is lower, and the bottom hole holding effect is smaller. It can not only effectively control the circulation loss of drilling fluid, increase the ROP, but also reduce reservoir damage , to protect low-pressure oil and gas reservoirs. Compared with pure gas drilling, the foam fluid has high viscosity and shear force, strong suspension and rock-carrying ability, which can effectively solve the technical problem that the gas drilling cannot be successfully constructed when the formation encounters water, and it is a fractured reservoir with a large loss. It is one of the ideal drilling techniques for the e...

AI Technical Summary

Problems solved by technology

However, since the liquid column pressure formed by the foam fluid in the foam drilling process cannot balance the collapse pressure of the formation, and the air foam fluid cannot form mud cake on the wellbore wall, water-sensitive shale such as water-swelling and water-collapsing When drilling in formations, it is very easy to cause wellbore instability, causing complex accidents such as pipe sticking, leading to the failure of drilling engineering. Therefore, it is particularly critical to use a strong inhibitory foam drilling fluid system for shale formations.

Chinese patent CN100535075C discloses a highly inhibited recyclable microfoam drilling fluid or completion fluid, the formula of which is bentonite + salt-resistant clay + soda ash + compound inhibitor SD-YZ + low-density viscosity-increasing agent SD-LVC + low-density viscosity-increasing Filtration reducer SD-LAC + low-density flow pattern regulator SD-LRC + low-density regulator constitutes SD-LDC, in which SD-YZ, SD-LVC, SD-LAC, SD-LRC, SD-LDC are composed of a variety of chemical The system is extremely complicated, which puts for

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