大庆三肇地区扶余油层储层敏感性分析

Analysis on Sensitivity of Fuyu Oil Reservoir in Daqing Sanzhao Area

大庆三肇地区扶余油层属于开发难度大的特低渗油藏,平均空气渗透率1.2×10-3μm2,且存在敏感性粘土矿物伊利石、绿泥石、蒙脱石/伊利石、蒙脱石/绿泥石混层。加深对该地区储层岩石各种敏感性认识,对优选适当的增产方法、优化工作液配方十分必要。采用实验室分析方法,对三肇地区扶余油层进行大量敏感性实验研究,实验表明该地区扶余油层存在中等速敏、中等偏强的盐敏、弱酸敏、弱碱敏及应力敏感性。临界流速为0.212 659 m/d、临界矿化度为4×104 mg/L表明需控制外来流体流速及添加适合粘土稳定剂来减少对储层伤害。临界pH值为9,表明工作液酸碱度都需要进行合理控制,预防二次污染。岩心加压过程、回压过程中最大渗透率损害系数分别为平均14.75%和9.2%,表明针对该地区的应力敏感性需注意调整合理的生产压差、开采速度和降压方式,为该地区油藏今后各种工作液配方的优化提供了依据。

Fuyu reservoir in Daqing Sanzhao area,with an average air permeability of 1.210-3μm2,is one of extremely low permeability reservoirs developed difficultly,which contains such sensitive clay minerals as illite,chlorite,mixed layer of smectite and illite and mixed layer of smectite and chlorite.It is necessary to acquaint oneself with sensitivity of various clay minerals in the reservoir in order to select proper production methods and optimize operating fluid formula.Adopted was laboratory analysis method to carry out a large number of sensitivity experiment researches on Fuyu reservoir of Sanzhao area and research results show that Fuyu reservoir is of medium velocity flow sensitivity,strong medium salt sensitivity,weak acid sensitivity,weak alkali sensitivity and stress sensitivity.Its critical flow velocity of 0.007 388 m3/d and critical salinity of 4×104mg/L show that extrinsic fluid velocity shall be controlled and proper clay stabilizing agent shall be added in order to decrease damage on the reservoir.The critical pH of 9 shows that pH value of the operating fluid shall be controlled properly in order to prevent secondary pollution.The average of maxium permeability loss factor of 14.75 % and 9.20 % respectively in core pressurization and depressurization process shows that production pressure differential,production rate and depressurization method shall be adjusted properly according to stress sensitivity in this reservoir,which provides the basis for future operating fluid formula optimization in this area.