海上油田大斜度井同心双管注水技术

A new water injection technology of concentric dual string in high-angle deviated wells of offshore oilfields

目前海上同心双管注水工艺存在着安全控制不可靠、内外管分层容易失效、封隔器解封不彻底等问题,造成洗井困难且影响油田正常生产。为此研究了新型同心双管注水工艺技术,该技术注水管柱相互独立,施工相对简单,外管附加载荷大大降低,注水三通道都能实现单独的安全控制。环空安全阀采用柱塞坐封方式并有备用注水通道,提高了安全阀的可靠性及使用寿命;内外管的分层采用组合盘根的形式,在容易失效部位采用组合盘根和内胶筒的双级密封方式,密封效果更加可靠;洗井则采用地面单独控制洗井滑套的方式,能够避免地层压差带来的洗井活塞自行开关,而且满足海上大排量反洗井的需求。该技术已在胜利海上油田成功应用10余口井,适用最大井斜为74.18°,层间最大压差为10.5 MPa,有效解决了大压差油层、大斜度井的有效分层注水难题。

At present,the water injection technology of concentric dual string used in offshore oilfields is faced with a series of difficulties.For example,the safety control is unreliable,the stratification of inner and outer string tends to fail easily,and well flushing is difficult due to incomplete unsetting of the packer.To solve these problems,a new water injection technology of concentric dual string was studied in this paper.In this technology,water injection strings are independent from each other,so the construction is relatively simple,the additional load on the outer string is reduced greatly and three water injection channels can all realize independent safety control.The annulus safety valve adopts the plunger setting mode and has a standby water injection channel,so its reliability and service life are improved.The pattern of combined packing is adopted for the stratification of inner and outer string,and two-stage sealing mode of combined packing and inner packer rubber is adopted at the easy-failure positions,which makes the sealing effect more reliable.For well flushing,the flushing sliding sleeve is controlled independently on the ground so as to prevent the formation pressure difference from leading to the self-switching of flushing piston and satisfy the needs of large-displacement inverse well flushing in offshore oilfields.This technology has been successfully applied in over 10 wells in Shengli offshore oilfield,and its suitable maximum well deviation and maximum interwell pressure difference are 74.18° and 10.5 MPa,respectively.In conclusion,this technology effectively realizes the separate layer water injection in the oil layers with large pressure difference and the high-angle deviated wells.