玉门青2-7井钻井液技术

玉门青2－7井一开井段砾石层成岩性差,胶结疏松,易卢井漏、井塌、沉砂;二开为砂泥岩互层,裸眼井段长,泥岩易水化膨胀,砂岩渗透性好易形成厚泥饼,砾岩、砂泥岩胶结差,井壁易坍塌,并存在石膏污染;三开为产层钻进,地层倾角大,裂缝发育,岩性为硬脆性泥岩,易发生掉块砖塌现象,井底温度高,根据该井地层特点、钻井工程要求和保护油气层的需要,一开使用“三高一适当”普通膨润土浆,防止了表层疏松砾石层的井漏、井漏;二开采用金属离子聚合物钻井液,该体系抑制能力强,防止了泥岩水化膨胀,具有良好的失水造壁性,防止了因砂岩地层渗透性好而形成的厚泥饼缩径,保证了长裸眼段的防塌及井下安全;三开选用金属离子聚磺屏蔽暂堵钻井液,该体系具有良好的失水造壁性,封堵防塌能力强,防止了油层段的剥落掉块垮塌,实现了近平衡钻井,保护了油气层。现场施工表明,该井钻井液技术满足了钻井、地质录井的需要,达到了保护油气层的目的。

Drilling fluid technology in Well Yumen Qing 2-7

In well Yumen Qing 2-7, due to the poor diagenetic grade and weak bonding, circulation lost, hole sloughing and sand setting are frequently encountered in gravel bed in the surface section ( 444. 5 mm); sandstone and shale are interbedded, open hole is too long, shale is prone to hydrated, thick mud cake is formed for high permeability of sandstone, conglomerate and sandstone are weakly bonded, hole collapse and contamination of gypsum exist in the second section (311 mm); such characteristics as high formation dip angle, fracture development, hard and fragile shale, high risks of sloughing and collapsing, and high bottomhole temperature has been in the production zone. According to the formation characteristics and drilling engineering requirements, conventional bentonite drilling fluid of high bentonite content, high filtration, high viscosity and shearing rate and suitable density (commonly referred to "3H1S") is used, to prevent lost circulation and hole sloughing from happening in the surface loose formation. Metal ionic polymer drilling fluid of strong inhibition is used in the second section, which effectively prevents hole shrinkage and mud making tendency because of shale hydration, while it has good wall building in high fluid loss, which prevents the hole shrinkage caused by the thick mud cake because of good permeability, and ensures the well stability in the long open hole. In the production zone, polysulfonate temporary shield plugging drilling fluid system is selected, in addition to the good wall building and plugging capability, it realizes the balanced drilling and formation protection. This drilling fluid technology can also meet the requirements of drilling and geological logging.