雁翎潜山油藏注氮气重力驱控气采油工艺

The gas control and oil production technology based on gravity drive of nitrogen injection in the Yanling buried-hill oil reservoir

华北油田雁翎潜山油藏通过注氮气在油藏顶部形成次生气顶,在气驱、重力分异作用下形成了2个流体界面(气油界面、油水界面)和3个流体分布带(人工气顶、含油富集带、水淹带)。顶部受效井井筒内气、油、水三相共存。为使油井正常生产,在原井存在永久封隔器的基础上开展了悬挂尾管开采的采油工艺试验,但效果较差。从生产实践、理论分析等方面探讨前期注氮气采油工艺的特点及存在问题,认为:油井生产过程中后期产层气液同出不可避免,由于氮气难以与原油混相,气体一旦进入井筒,则很快占据液流通道,使油井只出气不出液,且井口、套管和输油管线高压生产,存在安全隐患,顶部油井均被迫关井。为解决非混相垂直管流条件下油井生产问题,依据"U"型管压力平衡原理,开展了双管控气采油工艺研究,通过进行管柱优化,实现了气液分流、控气采油。

A secondary gas cap is formed at the top of the Yanling buried-hill oil reservoir of the Huabei Oilfield after nitrogen injection is carried out.Under the action of gas drive and gravity segregation,two fluid contacts(gas/oil contact and oil/water contact)and three fluid distribution zones(artificial gas cap,oil enriched zone and water flooded zone)are formed.Gas,oil and water coexist in the wellbores of the response wells at the top.In order to ensure the normal production of the oil wells,the oil production technology of liner hanging is tested in the original wells with permanent packer,but the test result is worse.In this paper,the characteristics and problems of the earlier oil production technology of nitrogen injection were discussed from the aspects of practical production and theoretical analysis.It is indicated that the simultaneous production of gas and liquid is inevitable in the middle and late stages of oil well production.Nitrogen can hardly mix with the crude oil,so once it flows into the wellbore,it will occupy the liquid flow channels quickly.As a result,the oil well produces only gas,but no liquid,potential safety hazards exit due to the highpressure production at wellhead,casing and oil transportation pipeline,and all the oil wells at the top are shut down unexpectedly.In order to solve the problems of oil well production under the condition of immiscible vertical pipe flow,the dual-tubing gas control and oil production technology was adopted according to the pressure equilibrium principle of U-shape tubing,and its pipe string was optimized.In this way,the gas and liquid shunting and the gas control and oil production are realized.