伊朗北阿扎德干油田沥青质沉积特征

Study on asphaltene deposition in North Azadegan Oilfield of Iran

伊朗北阿扎德干油田原油的四组分和气相色质联用分析表明,原油饱和烃碳链分布范围较广,直连烷烃主峰碳为C16,原油重质组分含量相对较高,石蜡组分少,芳烃组成非常复杂,其沉积环境为强还原和高盐度海相沉积环境;胶体不稳定系数及原油的流变性分析说明,该原油容易发生沥青质沉积;对伊朗原油沥青质初始絮凝点和沉淀量的研究发现,剂油比为0.21 mL/g时,伊朗原油沥青质开始发生絮凝,利用标度方程对沥青质沉积的预测表明,当剂油比为0.27 mL/g时,伊朗原油开始出现沥青质沉积,分子量较大的沉淀剂需要较大浓度才能引发沥青质沉淀,沥青质的沉淀量随沉淀剂分子量的增大而减小;分析注入不同体积天然气的特征化原油拟组分的变化情况,发现气举采油会导致沥青质的沉积初始压力升高,沥青质容易在井筒内沉积。

The north Azadegan oilfiled of Iran is an important overseas oil and gas exploration area of China. The asphaltene deposition features in this oilfield are studied to provide scientific basis for the future development. The four-component and GC / MS analyses of the crude oil samples from the oilfield show that: in the crude oil sample,the carbon chain of the saturated hydrocarbons has a wide distribution,the main peak carbon of the saturated straight-chain alkanes is C16,the content of heavy hydrocarbons is high,the paraffin content is low,the composition of the aromatic hydrocarbons is complex,and the crude oil is a typical oil originated from marine sediments formed under strong reduction and high salinity environment. The analysis of the colloidal instability coefficient( CI) and the rheology of the crude oil show that the asphaltene deposition easily takes place. The study on the initial flocculation point and the deposition amount of the asphaltene in the crude oil shows that: when the ratio of precipitant to crude oil is 0. 21 mL / g,the asphaltene in the crude oil begins flocculating. The prediction of the asphaltene deposition using scaling equation shows that,when the ratio of precipitant to crude oil is 0. 27 mL / g,the asphaltene in the crude oil begins depositing,for the precipitant with great molecular mass,more concentration is needed to make the asphaltene in the crude oil deposit,and the asphaltene deposition amount decreases with the increase of the molecular mass of the precipitant. The analysis of the pseudo components of the crude oil when injecting natural gas of different volume finds that gas lift production could make the initial deposition pressure of asphaltene rise and the asphaltene deposit more easily in wellbore.