乐安油田草4块沙四段储层沉积特征与非均质性研究

Reservoir sedimentary characteristics and heterogeneity of block Cao 4,member 4 of Shahejie formation in Lean Oilfield

储层沉积特征和非均质性已成为制约边际稠油油藏开发生产的瓶颈。利用地震、钻井、测井、岩心资料,对乐安油田草4块沙四段储层的沉积特征与非均质性及其对稠油开发的影响进行了研究。结果表明,研究区草4块沙四段发育两个三级层序,其岩石矿物学特征不同,沉积特征明显不同,含油性也不同;沙四上亚段为滨浅湖滩坝相沉积,而沙四下亚段为近岸水下扇沉积,其控制着95%的储量。储层渗透率变异系数为0.61～1.43,突进系数为2.21～5.41,渗透率级差大,层内、层间非均质性强,平面上非均质性相对较弱。综合评价出了有利的开发层段,其中沙四段4砂层组的3,4小层为有利开发层段,油层分布稳定,连通性好,可采用小井距强化注水面积井网或蒸汽吞吐热采开发,并采取适当的防砂措施。

Reservoir sedimentary characteristics and heterogeneity become the bottle neck restricting the production of marginal heavy oil reservoir block Cao 4 in Lean Oilfield. The sedimentary charateristics and heteyogeneity and their effects on the development of heavy oil reservoir were analyzed by the data of seismic, drilling, logging and core. The results show that member 4 of Shahejie formation in block Cao 4 of Lean Oilfield develops two sequences, which have different lithology minerals, sediment characters and oil potentials. The upper part of member 4 of Shahejie formation develops beach and bar facies, but the lower part develops submarine fan. The reserves of the lower part accounts for 95%. The reservoir permeability variation coefficient is 0.61 - 1.43 ; the onrush coefficient is 2.21 -5.41 ; the permeability ratio is large. The heterogeneity of internal layer and between layers is high, but in horizon it is relatively weak. The 3th and 4th layer of the 4th sandstone group are the preferable layers, which distribute stably and have good connectivity. Those layers can adopt enhanced little well-spacing water flooding area well-pattern or steaming soaking to develop and apply appropriate sand control measure.