Try the specialist programme and project mgt consultancies. Depending how much of the O&G business you were exposed to, it may also be worth targeting specialist consultancies to the O&G industry. These are the organisations which are most likely to be able to use your experience. However, you need to make sure you're looking at roles at an appropriate level - for example, when you honestly appraise your own CV, how much of your experience has been at professional or managerial level? If the answer is "not much", you may be best off applying as a graduate where prior experience is not assumed.