HOUSTON, Dec 8 (Reuters) - The shift of motor fuel production to net-zero carbon emissions by mid-century will lead oil refiners to overhaul future projects and spending, said analysts and executives on Wednesday. “The profile of the projects will be changing,” said Ethan Phillips, a partner with consultancy Bain & Co., at a Houston energy conference. “We’re looking at smaller, more modular projects.’Citing figures produced by analysts at IHS Markit, Phillips said about 70% of the estimated $164 billion to be spent on capital projects in the 2030s will go to biofuels and carbon reduction, most in the United States and Europe. “Existing refinery capex is going to look different,” Phillips said, referring to spending on major projects. “There will be more modular projects and more emphasis on short-cycle projects.”Modular components reduce construction challenges but increase the importance of planning projects, said Shaker Asiri, a lead project engineer with Saudi Aramco, the world"s largest oil producer. In one project, Asiri said a 200-foot flare tower that burns off unwanted processing gases was constructed with modular components. “It was like putting Legos together," he said. Expansion of existing refineries, called brownfield projects, to add biofuel and carbon reduction systems at U.S. and European refineries, likely will be more costly than generally understood, Asiri said. “Once you start doing brownfield projects, you realize the cost is much more than greenfield projects,” he said.