Towards the carbon neutrality, the traditional fossil fuel-based energy supply in oilfield urgently needs to be replaced by the integrated energy systems (IES) based on zero carbon and negative carbon technologies. However, existing studies have not yet to address the challenge of optimization design for negative carbon IES under flexible load conditions in oilfield. Therefore, three scenarios are proposed in the present study, an IES integrating renewable energy and negative carbon technology (Case 2), further incorporating source-load interaction (Case 1) and the conventional energy system (Case 3). A planning and operational optimization model are developed to validate the advancement of the system and the effectiveness of the source-load interaction mechanism. The obtained results show that: i) The oilfield IES increases net present value (NPV) by 10.26% and 1.35% in Case 1 and Case 2 comparing with Case 3 respectively, supporting a cost-effective transition. ii) All three scenarios realize negative-carbon operation, and the net emission reductions of Case 1 and Case 2 are 9.20% and 8.20% higher respectively comparing with Case 3. iii) The Case 1 with source-load interaction improves the performance in economic, decarbonization and reliability by 9.04%, 1.00% and 6.67% respectively compared to the Case 2. Therefore, the present study offers a more efficient solution to the trilemma in the low-carbon transition in oilfield energy system.