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This multidisciplinary paper presents microbial Huff and Puff project results with objectives: 1) to understand the mechanisms through relating laboratory work results, field implementations and a history matching process during reservoir simulation (2) to seek reliability of the microbial Huff &Puff based on improvements of the production performance parameters. After a thorough screening work was done, detail laboratory works produced fluid samples from selected wells was conducted, implementation programs were designed, and a set of equipment consisting of a cultivation tank, a mobile laboratory, and other supporting facilities was installed at the field. The implementation basically involves three stages: (1) preflush, cultivation solution, and post flush (2) injection of cultivation solution and post flush, and (3) injection post flush. Finally, this project conducted a 6-month monitoring program of microbe population and compositional analysis of the produced fluid samples, and production performance analysis of wells production data. The overall growth of bacteria had increased from 2×103 CFU / mL to 5×106 for 176 days in Well MJ122, on the other hand, Well MJ-125 can reach much higher up to 500×106 bacteria (CFU/ml) in 122 days. Using the GC/MS composition analysis for semi-quantitative analysis with standards internal reference marker ratio of Pr/Ph shows monthly biodegradation samples percentage before and after application up to about 34% at the 3rd month of monitoring. The well MJ-125 Structure Analysis of Bacteria Community resulted from Single Strand Conformation Polymorphism (SSCP) Method indicated that the number of Operational Taxonomy Unit (OTU) change during the production was relatively stable and this correspond to their Sorensen Index values. But, MJ-122 well indicated unstable community structure, however, the interaction between microbes which were injected with indigenous microbes was not competitive. The wells water cut versus gross rate profiles show that the MJ-122 water cut drop occurs at low production rate, whereas, the MJ-125 water cut drop occurs drastically both in low and high production rates. The well MJ-125 average oil rate gain is about 20%. However, both wells show peculiar production profiles by depicting a cycle of "a valley of low values". Finally, a history matching process supports understanding of the mechanisms.