懸掛式獨立中心管氣舉反循環系統在天津地熱井施工中的應用研究

黃賢龍 李志杰 劉贊 楊忠彥 董秋生

摘 要：隨著天津地區深部地熱資源開發力度的加大，地熱井鉆探的深度和鉆進難度越來越高。特別是天津地區古生界奧陶系灰巖和薊縣系霧迷山組白云巖等漏失嚴重地層，因巖屑難以上返，無法建立有效的循環，容易造成埋鉆，卡鉆等事故。本文針對以上難題，引進反循環鉆井工藝，以常規氣舉反循環設備為基礎，并針對其氣密性差、造價高、使用保養成本高、參數難以控制的缺點進行改進，研發一套新型的氣舉反循環鉆井系統工具，并進行實鉆試驗，成功鉆穿天津地區霧迷山組三四段地層，解決天津地區破碎地層難以鉆穿的難題，并獲得相應的鉆進參數，為今后天津地區地熱井反循環鉆進提供經驗和借鑒。

關鍵詞：氣舉反循環；地熱井施工；鉆進參數；霧迷山組地層；地熱能源

中圖分類號：TU991.12 文獻標識碼：A 文章編號：1671-2064（2018）22-0151-02

1 Introduction

Under the call of national energy saving and emission reduction， geothermal resources are more and more popular with the advantages of no pollution， no emission， recycling and so on. In recent years， the development of deep thermal reservoir in Tianjin area is increasing， the depth of geothermal well drilling （Ma Z P et al.， 2008） is getting deeper and deeper， and the drilling difficulty is becoming more and more challenging. Due to the particularity of underground geological conditions in Tianjin area， it is difficult to drill through the broken strata in bedrock by typical circulation drilling technology. Air lift reverse circulation drilling technology has been mature both domestic and abroad （Xu L W et al.， 2009， Xiong L et al.， 2014， Wang Y G et al.， 2009）， but the conventional double-wall drilling pipe reverse circulation equipment is difficult to carry large pieces of lithic debris up and back due to poor gas tightness， so it is difficult to drill through the broken strata in Tianjin area. In addition， due to its high equipment cost， difficult maintenance， relatively poor drilling efficiency as compared to the positive circulation， so the air lift reverse circulation drilling technology has not been popularized in Tianjin area.

In this paper， based on the improvement of conventional double-wall drilling pipe reverse circulation （Chen Y et al.， 2009） equipment， a set of new air lift reverse circulation drilling system tool， which is suspension independent central tube gas lift reverse circulation system， has been developed. The equipment overcomes the disadvantages of poor air tightness， high cost， high maintenance cost and difficult to control the parameters. It has been successfully used in the construction of a geothermal well in Tianjin， and successfully drilled through the third and fourth stratum with broken strata in Wumishan， and achieved good results.

2 Design of suspended Independent Central Tube Air lift reverse Circulation system

2.1 Design Principle

In order to solve the disadvantages such as high cost， poor airtight and difficult parameter control of double-wall drill pipe reverse circulation system， the following principle should be followed in the design phase： for positive circulation drilling tool， the anti-circulation system module should be installed. It has the function of reverse circulation， and the conversion of positive and reverse circulation drilling tool structure is simple： it does not destroy the original drilling tool structure and does not affect the service life of the original drilling tool； （3） reliable performance： to ensure reliable airtight and sufficient strength of the system device is economical and practical； to ensure the stability of the system device， to reduce the cost as much as possible， which is conducive to popularization and application.

2.2 Process structure design

Independent center pipe and concentric installation of positive circulation drilling tool to form two channels necessary for reverse circulation. The top of the center tube is suspended from the positive circulation faucet by special parts and can be rotated freely through bearing.

Remove the gooseneck pipe of the positive circulating faucet， install the suspension rotating assembly， connect the compressed air intake pipe， connect the outlet interface with the high pressure hose， connect the assembly with the central pipe， air water mixer， and the central pipe string through the square drill pipe， A double-wall pipe system is formed with the drill pipe， and the whole drilling tool structure is connected with the reverse circulation special drill bit at the bottom of the whole drilling tool structure， so that the original normal circulation drilling tool structure is modified to form a set of air-lift reverse circulation drilling tool structure （see figure 1）.

3 Practical Drilling Test and Analysis of drilling parameters

practical drilling test has been carried out to successfully drill through the third and fourth.

In this drilling test， a geothermal well with a depth of more than 3000 meters is designed for the first and second stratum of Wumishan in a certain area of Tianjin. In the construction of this well， the broken strata of the third and fourth stratum of Wumishan was drilled， and a large number of leakage of drilling fluid resulted in the lithic debris being unable to return， too much debris accumulated in the well， and the positive circulation could not be continued. The basic data of geothermal wellbore structure are shown in Table 1.

The reverse circulation drilling well is the third and fourth stratum of Wumishan of Jixian system， which is mainly yellow and gray dolomite. At the bottom of the third stratum， there are 7 layers of red beds with purple red， brick red dolomite and muddy dolomite. The lower part is covered with gravel quartz sandstone thin layer. In the drilling process， there are about 72m broken strata in the four sections of drilling， which often collapse and lose seriously at the same time.

4 Conclusion

1）The components of the air lift reverse circulation system are modularized， which is convenient for installation and maintenance， and does not need to change the drilling rig. The conversion of positive circulation and reverse circulation technology is convenient and quick.2）Compared with the traditional double-wall reverse circulation system， the cost of the system has been greatly reduced. From the economic point of view， the popularization and application of the system has a very obvious advantage.3）The system has the advantages of good air tightness， controllable drilling parameters and higher sinking ratio， which is more suitable for the geological conditions of the complicated Wumishan formation with serious leakage than the traditional double-wall drilling pipe reverse circulation system.

References

[1]Ma Z P，Pang H，Wang Y H，et al.2008.Geothermal well drilling and completion in Tianjin Area. Exploration Engineering （Rock & Soil Drilling and Tunneling），12：9-11.

[2]Xu L W，Liu Z R，Zhao M J，et al.2009.Alternative process air drilling technology and its new development.Exploration Engineering （Rock & Soil Drilling and Tunneling），36（10）：8-14.

[3]Xiong L，Zhang X L，Xiong J Q， et al.2014. Preliminary analysis on influence factors of air-lift reverse circulation drilling efficiency to large diameter engineering well.Exploration Engineering （Rock & Soil Drilling and Tunneling），41（5）：42-45.

[4]Wang Y G，Xiao H L，Xie L S.2009. Application of airlift reverse circulation drilling in Jingre 164# well of 3512m depth.Exploration Engineering （Rock & Soil Drilling and Tunneling）， 36（2）：9-11.

[5]Chen Y， Duan D P.2009.Application of airlift reverse circulation drilling in Baoli ZK3 deep geothermal well of Guizhou.Exploration Engineering （Rock & Soil Drilling and Tunneling）， 36（4）：23-28.