ABUJA (Reuters) -Nigeria’s Senate said on Wednesday it will investigate oil company Shell Plc over alleged illegal extensions of oil exploration leases and is seeking a refund of $200 million which it said accrued over the period. The upper house of parliament said a seven-member committee has been mandated to investigate oil exploration leases granted to Shell’s Nigerian division from 1959 to 1989 and from 1989 to 2019 under a joint venture agreement with state-owned NNPC. The Senate said the decision to investigate was following the non-payment of $200 million accruals from Shell’s oil minin…