The need to reduce the environmental risk from shale-oil drilling is boosting the allure of Poseidon Concepts Corp. as takeover target. Poseidon may make sense for Schlumberger Ltd. and Halliburton Co., the world’s two biggest oil services providers, Roomberg and Haywood’s Geoff Ready said. Poseidon, split off from Open Range Energy Corp. so it could rent out so-called frack tanks to other producers, may also attract interest from potential buyers, according to Haywood’s Ready, a Calgary-based analyst. The tanks are used to store fresh water before it’s pumped into the well for fracking. They then hold the tainted water after it is pumped back out and before being trucked away or recycled by another company.