Asphaltene precipitation is a sophisticated issue in the upstream oil industry, worldwide, and has detrimental effect on a verity of production processes in oilfields; it damages the properties of the reservoir and causes an unfavorable and significant decrease in oil production. Many oil reservoirs encounter asphaltene precipitation as a major problem during natural production. It is desirable to predict and investigate the precipitation behavior of asphaltene in different pressure temperature conditions. In spite of numerous studies to predict asphaltene behavior, the effect of temperature on asphaltene precipitation during pressure depletion at reservoir conditions is still obscure in the literature. In this work the PVT data as well as experimental data of asphaltene precipitation at reservoir conditions of two Iranian heavy and light oil samples are used, and the asphaltene precipitation and deposition envelops (APE and ADE) of the oils are developed.