Original Message

If you are a company hired by another company to conduct those patrols, then it likely 135 because you are holding out to the public to fly air commerce.

If you are conducting those patrols for your own company, it can be done Part 91, but the pilot needs a Commercial ticket if he is being paid as a pilot.

If your company contracts with another company privately, and not with others, then it can be considered a private conveyance and done under a Part 91 Operators Specification, but it will need to be FAA (FSDO) endorsed.