NOVELTY - Method (M1) of making a synthetic consortium, comprises e.g.: (a) obtaining at least two sample from at least two different sources, where each sample comprises many microbes; (b) determining the microbial composition and abundance of the samples, where the abundance of each observed microbe is recorded for each sample; (c) performing a correlation analysis of abundances of one microbe in at least two samples to abundances of another microbe in the two samples; and (d) repeating step (c) for at least one additional pair of microbes in samples.    USE - The method is useful for making a synthetic consortium or identifying and making a synthetic microbial consortium (claimed), which is useful for improving methylotrophic biogas formation in situ in a subsurface carbonaceous formation, preferably simulating biogas in subsurface conditions.    DETAILED DESCRIPTION - Method (M1) of making a synthetic consortium, comprises: (a) obtaining at least two sample from at least two different sources, where each sample comprises many microbes; (b) determining the microbial composition and abundance of the samples, where the abundance of each observed microbe is recorded for each sample; (c) performing a correlation analysis of abundances of one microbe in at least two samples to abundances of another microbe in the two samples; (d) repeating step (c) for at least one additional pair of microbes in the samples; (e) identifying a group of at least two microbes, whose abundance correlation to one another is greater than other microbes in the samples; and (f) assembling a synthetic microbial consortium by physically combining at least two microbial cultures of the identified microbes. An INDEPENDENT CLAIM is also included for a method (M2) of identifying and making a synthetic microbial consortium, comprising: (a1) obtaining many samples comprising microbes; (b1) determining the abundances of a many microbes in many samples, where the abundance of each microbe is recorded for each sample; (c1) compiling a numerical abundance of an environmental parameter of many samples; (d1) performing a correlation analysis of the abundance of one microbe in many samples to the abundance of the environmental parameter in many samples, where the correlation analysis provides a comparison between the abundance of the microbe to the abundance of the environmental parameter; (e1) repeating step (d1) for at least one additional microbe in the samples; (f1) identifying at least two microbes whose correlation to the environmental parameter is greater than other microbes in many samples, (g1) obtaining microbial cultures of at least two identified microbes; and (h1) combining the microbial cultures of the identified microbes, thus making a synthetic consortium.