原油沥青质的沉积条件及其控制

Precipitation condition of crude asphaltene and its controlling

原油温度、压力和组分的改变均会引起沥青质发生絮凝和沉积,造成储层损害.沥青质沉积热力学预测模型可以更直观、方便地确定沥青质的沉积条件.建立了一种沥青质沉积条件的预测模型,该模型将沥青质沉积相视为固相,按液-固相平衡来处理沥青质的沉积问题,根据井筒流体组成和地层性质等资料,估算原油沥青质开始沉积的压力,并提出相应的井下热力学控制条件.利用该模型预测了渤海SZ36-1油田具有代表性的3口油井的原油沥青质发生沉积的初始压力,结果表明,随着压力不断下降,原油中的沥青质在沉积初始压力处开始发生沉积,且该压力比地层温度下的原油饱和压力高出2～4 MPa,这为预防油井发生沥青质沉积具体措施的制订提供了理论依据.

Changes in temperature, pressure and components of crude oil will cause flocculation and precipitation of aspahltene, which causes reservoir damage, The precipitation conditions of aspahltene can be predicted conveniently and directly by the thermodynamic model, On the basis of the collection and analysis of the field and experimental data, a model to predict the onset pressure of the crude asphaltene precipitation was established. In this model, precipitated asphaltene was treated as solid phase, according to the data such as liquid composition in wellbore and formation characteristics, asphaltene onset precipitation pressure could be estimated conveniently through liquid and solid phase equilibrium calculation. The results in Bohai SZ36-1 Oilfield show that asphaltene precipitation occurs with pressure dropping and under the onset precipitation pressure, and this pressure is more 2 MPa to 4 MPa than the saturation pressure, The downhole thermodynamic conditions to prevent and control asphaltene precipitation were presented.