The heating efficiency of steam in the development of heavy oil by steam injection is an important factor influencing the development effect. In order to improve the evaluation process of the heating efficiency during the thermal recovery development of offshore thick-layer heavy oil reservoirs, typical core samples from the LD block in the Bohai Sea were selected, and a quantitative evaluation of the thermal efficiency of the target oilfield was systematically carried out from three dimensions: physical experiments, theoretical evaluation, and numerical simulation. Through physical property testing experiments, the variations of thermal conductivity and specific heat capacity of different rock types with temperature were determined. The thermal conductivity and heat absorption capacity of the reservoir rocks were analyzed, and the thermal diffusivity of the reservoir rocks was calculated and analyzed. Then, an evaluation method for reservoir heating efficiency was established based on the principle of energy conservation. The CMG numerical simulation method was used to analyze the characteristics of thermal efficiency changes during cyclic steam stimulation (CSS), steam flooding(SF), and steam-assisted gravity drainage (SAGD) development in thick layer heavy oil reservoirs. The results show that the thermal diffusivity of sandstone and conglomerate in the LD block is higher than that of mudstone. The temperature in the sandstone and conglomerate propagates faster, allowing more heat to be applied to crude oil. Compared to SF, CSS has a lower heat loss rate in the early stages of production. As production continues, the heat loss rate increases. Ultimately, the thermal efficiencies of CSS and SF are 67.6% and 31.1%, respectively. Under homogeneous reservoir conditions, the thermal efficiency of SAGD is 43.3%. Reservoir heterogeneity, the presence of bottom and edge water, or continuous interlayers reduce thermal efficiency by 2.6% to 15.3%. This study provides systematic guidance for the systematic evaluation of the thermal efficiency of different types of thick-layer heavy oil reservoirs and the efficient development through thermal recovery methods.