Laboratory investigations on the effects of surfactants on rate of penetration in rotary diamond drilling

• The effects of three surfactants on the rate of penetration were investigated.
• The properties of the surfactant solutions and rock–solution interfaces were studied.
• A mechanism of fluid–rock interaction during drilling was proposed.

Laboratory investigations were carried out on sandstone to research the effects of three representative surfactants, including Triton X-100, sodium dodecyl benzene sulfonate (SDBS) and 1-hexadecylpyridinium chloride (CPC), on the rate of penetration (ROP) in the process of rotary diamond drilling. Properties of the sandstone, the surfactant solutions as well as the solution–sandstone interfaces were determined to study the influences caused by these surfactants. The results showed that either Triton X-100 or SDBS can increase the ROP while the effect of CPC is marginal. Both Triton X-100 and SDBS can help the flushing water to spread on the sandstone surface fully. SDBS and CPC can reduce the indentation hardness of the sandstone to some degree. A detailed discussion was presented in order to understand these results in depth, and then a comprehensive mechanism was proposed for explanation. Spreading behavior of the flushing media, Zeta potential, rock-breaking mode and rock properties all contribute to the effect of a given chemical environment on ROP. At various stages of drilling process, the roles performed by the chemical environment may be drastically different.

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