Community Distribution of Biofilms along a Vertical Wellbore in a Deep Injection Well during Petroleum Production

Abstract

In petroleum production, microbial investigations are essential for microbial-induced corrosion (MIC) control and enhanced oil recovery (EOR) processes. It is suggested that microorganisms can attach to the inner wall of pipes as biofilms, which are more stable and could cause more serious corrosion than planktonic microorganisms in the water phase. At present, research on the biofilms during oil production is mainly focused on the surface pipelines, while few reports have directly investigated biofilms in vertical deep wells. Therefore, in this study, wellbore biofilms were sampled during well workover from several well-tube segments corresponding to different original depths (approximately 0, 840, and 1330 m). The injected water was sampled as well. The results of the 16S rRNA gene library sequencing showed that the biofilms and water-phase communities were distinct (dissimilarity of 0.56–0.64), although they shared 64 OTUs. At the phylum level, the relative abundance of Proteobacteria was 74.65% in the water phase and only 7.86–27.41% in the biofilms. The dominant phylum, Firmicutes, was 6.03–41.21% in the three biofilms, while only 1.16% in the water phase. With increasing depth, the biofilm communities became more diverse (Shannon index of 3.43–4.21), more anaerobic, and more thermophilic possibly due to the depleting oxygen and increasing temperature in samples from the deeper well. For instance, the relative abundance of anaerobes (archaea and strict anaerobic bacteria) in biofilms increased from 18.32 to 40.53%. Thermophilic bacteria (such as Kosmotoga) increased from 6.65 to 15.82%. Among methanogens, hydrogenotrophic genera (such as Methanobacterium and Methanolinea) increased from 3.66 to 9.68%. This study revealed the structural differences between water-phase and biofilm communities in the well, and the depth-dependent distribution of the biofilm communities. These results improved the understanding of microbial ecology in wellbores, which will benefit microbial activity control measures applied in oil production processes, including MIC and oil recovery.

Optimized Design of Oil-Water Separator for Injection and Production in the Same Well

“…Downhole oil-water separation [1][2][3][4][5][6] (DOWS) is a new technology, which solves the problems of high oil well production and large separation workload in the development of high-watercut oilfields, addresses the huge investment and energy loss caused by water injection, and shows remarkable economic benefits and environmental protection effects. At present, there are two basic ways of DOWS: hydrocyclone separation technology and gravity separation technology [7][8][9][10][11][12]. According to the separation principle similar to multicup isoflux gas anchor, the multicup isoflux oil-water separator was designed, which can solve the problem that the existing downhole centrifugal oil-water separator has poor separation effect and cannot be applied on a large scale.…”

Well Rehabilitation via the Ultrasonic Method and Evaluation of Its Effectiveness from the Pumping Test

“…Physical methods include attaching a brush to a drill with high pressure jetting, hydrofracturing, and surging. In recent years, one of the technologies categorized as a physical method, the ultrasonic method, has begun to be used for well rehabilitation [17,18]. This relatively new technology was previously studied and applied to oil wells [19][20][21][22][23][24][25] but is also now applied to water well rehabilitation [26][27][28][29].…”