正韵律厚油层剩余油分布模式及水平井挖潜——以孤岛油田中一区Ng5~3层为例

Distribution mode of remaining oil and tapping the potential by horizontal wells in thick positive-rhythm oil layers-taking Ng5~3 layer in Zhongl area of Gudao oilfield.

孤岛油田是一个高渗透、高粘度、高饱和的河流相正韵律沉积的疏松砂岩油藏,Ng3-4砂层为曲流河沉积,Ng5-6砂层为辫状河沉积。运用室内实验、矿场测井和动态监测、油藏数值模拟技术,根据Ng5-6砂层正韵律厚油层层内夹层分布特征及实际注采状况,建立了水井钻遇夹层、油井钻遇夹层、夹层在油水井之间三种类型12种注采模式,研究了不同注采模式下的剩余油分布规律及层内夹层对剩余油的控制作用。结果表明,层内夹层对剩余油分布的影响程度取决于夹层厚度、延伸规模和垂向位置。针对孤岛中一区Ng53正韵律厚油层地质特征和特高含水期顶部剩余油富集规律,提出了实施水平井挖潜的原则,并优化了水平井位置、水平段长度、生产压差和提液时机等参数。矿场实施16口水平井,取得了较好的效果,在井区综合含水率已达93.7％,采出程度高达45.3％的情况下,水平井初期产油量达18-33.5t/d,是周围直井的3-4倍,综合含水率只有38.8％,比周围直井低30％-50％。

Gudao oilfield is a loose sand oil reservoir deposited by positive-rhythm fluvial facies with high permeability, high viscosity and high saturation. Ng 3-4 sand is deposited by meandering river, and Ng 5-6 sand is deposited by braid river. Applying laboratory experiment, field logging, dynamic monitoring and reservoir numer-ical simulation ,and based on distribution characteristic of intraformational interbed in thick positive-rhythm oil layers in Ng 5-6 sand and actual injection-production situation, twelve injection-production modes with three types are built for interbed drilled in water wells, in oil wells and between water and oil wells. The remaining oil distribution rule under different injection-production modes and the control effect of intraformational interbed on the remaining oil were studied. The results show that the influencing degree of the intraformational interbeds on the remaining oil depends on the thickness, spread scale and vertical position of the interbeds. According to the geologic characteristics of the Ng53 thick positive-rhythm oil layers and top remaining oil enrichment rule during extra-high water cut period in Zhong 1 area of Gudao, the principle of tapping the potential by horizontal wells is put forward. The parameters are optimized which include the position of the horizontal wells, length of horizontal section, producing pressure differential, timing of liquid lifting and son on. Field application achieved good results in 16 horizontal wells. When composite water cut is up to 93. 7% and recovery percent of reserves is high up to 45. 3% , initial oil production rate of the horizontal wells is up to 18-33.5t/d, which is 3-4 times of the vertical wells around ; composite water cut is only 38. 8% lower 30%-50% than the vertical wells a-round.