Journal of Petroleum & Environmental Biotechnology

Characterization of the corrosion of oilwell cement exposed to H2S under high-sulfur gas reservoir conditions

3^rd World Congress on Petrochemistry and Chemical Engineering

November 30-December 02, 2015 Atlanta, USA

Gu Tao, Guo Xiaoyang , Li Zaoyuang, Huang Sheng and Cheng Xiaowei

Southwest Petroleum University, P.R. China

Scientific Tracks Abstracts: J Pet Environ Biotechnol

Abstract:

H2S is an acidic and toxic gas and the corrosion of H2S on oilwell cement is considered to be a great challenge for wellbore integrity and environmental safety in the exploitation of high-sulfur gas reservoir. In our work, an unidirectional sample was designed to simulate the actual downhole condition, and the corrosion performances of oilwell cement exposed to humid H2S gas and H2S-rich brine were investigated using designed unidirectional samples. Compressive strength, microhardness, porosity, gas permeability, SEM, EDS, and XRD analyses were conducted to compare the dissimilarity of H2S attack in two exposure scenarios. The experimental results show that the corrosion degree of cement exposed to humid H2S gas was lower due to a dense gypsum layer formed on the cement surface; this layer inhibited inward penetration of H2S by blocking diffusion. On the contrary, a porous and loose amorphous silica gel section formed on the headspace of brine-exposed cement for dissolution and migration effects of brine, which facilitated the penetration of H2S to the interior of cement. The degradation mechanism of cement and the effects of exposure scenario on cement properties are proposed.

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