摘要
深部钻探是人们认识地球、建立地壳深部通道最直接的方法。同时,我国资源供需矛盾显著,浅部资源逐渐枯竭,因此深部钻探势在必行。在地质勘探中钻孔分类的标准是:浅孔:0-300米,中浅孔:300-600米,中深孔:600-1200米,深孔:1200-2500米,特深孔大于2500米。绳索取心钻探工艺,由于其辅助时间少,取心质量好,效率高等优势得到钻探工作者的广泛认同,但泥浆技术问题也较为突出,在很大程度上制约了绳索取心钻进工艺的发展,本文针对深部钻探绳索取心钻井液技术问题进行了探讨和研究。西藏罗布莎铬铁矿区科学钻探孔是《大陆科学钻探选址与科学钻探实验》7口预导孔的第一个钻孔。它的主要成果是揭示铬铁矿矿集区深部地质构造和成矿岩体的延深和展布,评价罗布莎岩体深部的铬铁矿矿产和雅鲁藏布江缝合带中有关超镁铁岩体的铬铁矿矿产的远景;查明罗布莎岩体和其所在的超镁铁岩带的成因和构造背景。罗布莎含矿超基性岩体沿雅鲁藏布江的谷底分布,严格受雅鲁藏布江构造带的控制。在成岩期和成岩后期都遭受了强烈的构造运动,形成了一些列复杂的构造变形。直接表现为区内矿床发育,地层复杂,上部卵砾石直径大,胶结性差,下部超基性岩破碎以及蚀变(蛇纹石化)严重,对钻探的影响是岩心采取率低,全孔不间断存在漏浆、难钻、坍塌等问题。在地质构造发育、岩石破碎的地层钻进中,孔壁稳定是关键。主要从两个方面研究孔壁稳定问题:孔壁周围应力分析和钻井液的物理化学性能分析。当作用于钻孔侧壁岩石的压力大于静液柱压力时,则孔壁很有可能发生破坏或坍塌,由此就可以推导出静压平衡条件下钻井液应采用的合理密度。另外,钻井液对孔壁岩石的水化、环空上返速度过大对孔壁的冲刷以及提下钻具时产生的激动压力都有可能破坏孔壁的稳定性。根据地层的漏失特征、通道值以及漏失强度将地层分为3大类12小类,根据类型的不同建议采用的堵漏方式也随之改变。针对罗布莎破碎地层建立了钻井液的粘度与破碎地层的厚度的对应关系模型,并初步提出钻井液护壁的极限判据。从上世纪70年代初研究与发展绳索取心钻探技术到现在,绳索取心钻探技术广泛应用于岩心勘探。尤其是当钻遇硬度级别为6-9级岩石、钻孔深度大以及钻头寿命长时,绳索取心钻探最能发挥其优势。小口径绳索取心钻井液也面临一系列的瓶颈问题,主要包括钻杆内壁容易结垢,钻孔环空间隙小,钻井液润滑性差,循环阻力大,携粉能力低,滤失量高,护壁效果不好等问题。要解决好这些问题,必须提高钻井液的性能。经验分析通过降低机械钻速、加强控制固相含量,采用无固相钻井液等方式能够防治钻杆结垢;matlab分析循环压耗模型得出:适当加大钻头的直径,提高环空间隙0.5mm,能够降低循环压力2倍左右;聚乙烯醇与O型润滑剂配伍,极压润滑仪测试的润滑系数降低0.6倍:聚乙烯醇与PAC、XC等剪切稀释性能好的高分子聚合物配伍,提高钻井液的动塑比,加强携粉能力;聚乙烯醇与磺化沥青、褐煤树脂等处理剂配伍能够将滤失量降低到8m1以内。根据西藏罗布莎地层及现场钻井液的使用情况,研究低粘、低切、润滑性能好、抑制性强、携岩能力好、具有剪切稀释性、优良造壁性作用的PVA无固相钻井液,可以较好的解决钻井过程中的存在的问题,保证钻孔安全、提高钻进效率。通过大量现场和室内实验研究,PVA无固相钻井液配方如下2.5%PVA 0.05%PAC 3%SPNH 0.5%O型润滑剂。具有以下优点:(1)良好的流变性:钻井液低粘度、低切力,适合绳索取心钻探环空小间隙,有利于提高钻速、减小循环阻力;(2)显著的护壁效果:通过浸泡实验与常用的低固相钻井液相比较,PVA无固相钻井液中浸泡24h过后的岩心没有变形或者膨胀,而且再放入清水中浸泡7d依然不变形、不坍塌;(3)优良的抑制性:通过页岩滚动回收率实验和高温高压线膨胀性实验,总结出PVA无固相钻井液能很好的抑制泥页岩孔壁膨胀、分散;(4)滤失量小,润滑性能好:褐煤树脂主要在钻井液中起降滤失效果,且作用明显,且其润滑效果也较为出色,已经能够满足一般的润滑要求。当钻孔加深,循环阻力变大,润滑效果要求强时,可添加O型润滑剂,能够明显增强润滑效果;(5)携粉能力佳:通过自行研发的钻井液悬渣能力测试仪器,测试得出PVA无固相钻井液的悬渣效果虽然没有低固相钻井液好,但就无固相钻井液来说,PVA无固相钻井液动塑比较高,能较好的悬排金刚石钻头研磨下来的岩粉,清洁孔底。
Deep drilling is the most direct way for people to understand the Earth and to establish a passage in deep crust. Meanwhile, there is a significant imbalance between supply and demand of resources because of the depletion of shallow resources, leading to Imperativeness of deep drilling. The classification criteria of boreholes in geological exploration is that borehole depth between 0 and 300 m is called a shallow hole, that between 300 and 600 m is called a medium-shallow hole, that between 600 and 1200 m is called a medium-deep hole, that between 1200 and 2500 m is called a deep hole, and that above 2500 m is called a super deep hole. Wire line coring process costs less auxiliary time, gets high cores quality, and is efficiency, as well as it is preferred to because of its advantages by drilling workers, the mud problem is prominent in wire line coring process, which is a restriction of the development of the process. In this paper, drilling fluid technologies are discussed and studied of small diameter wire line coring in deep drilling.The scientific drilling hole in Tibet Luobusha chromites mining area is the first of the seven boreholes in the "Continental Scientific Drilling Site Selection and Pilot Holes ". Its main goals are to reveal the deep geological structure and the extension and distribution of rock mass, to evaluate the prospect of Luobusha chromites and the chromites in ultramafic rock in Brahmaputra suture zone, and to find out the genesis and structure background of Luobusha rock and of the ultramafic rock zone it exists in. The ultrabasic rock of Luobusha in Tibet alone the Yarlung Zangbo River by the valley of the distribution strictly controlled by the tectonic zone of the Yarlung Zangbo River. Late in the digenetic and digenetic have suffered intense tectonic deformation, formed a series of complex tectonic deformation. It directly expressed as the development of regional deposits, complex formation. The upper parts of the gravel sediment diameter, which is poor cementation, the lower ultrabasic rock crushing and serious alteration (serpentinization), impacting the drilling with poor core recovery, and existing uninterrupted problems of mud leakage, drilling difficulties, collapse in the whole holes.Drilling in the formation of geological structural development and rock broken, hole stabilization is the key. Mainly researched from two aspects of hole stabilization problems:the stress analysis around the hole wall and analysis of physical and chemical properties of drilling fluids. As the pressure for drilling the rock wall is greater than hydrostatic pressure, the hole wall is likely to damage or collapse, which can accurately calculate the reasonable density of the drilling fluid under hydrostatic equilibrium conditions. In addition, the drilling fluid on the pore wall rock hydration, hole erosion caused by too large velocity in annulus, and the pressure generated by raise or down the drilling tools are likely to undermine the stability of the hole wall. According to the leakage characteristics of formation, the channel intensity values, and Strength loss will be divided into 3 classes and 12 subclasses, and the way of plugging along with the change in classification. Relationship model about drilling fluid viscosity and the thickness of strata corresponding breaking was established for Luobusha Stratum, and the extreme conditions what use drilling fluid to protect holes was proposed preliminarily.From the early research 70s research and development the drilling technology of wire line coring to now, the drilling technology of wire line coring was widely used in core drilling. When drilling the rock of the hardness level is 6 to 9, drilling is deep and long bit life; core drilling can best play to their strengths. However, deep drilling small diameter wire line coring technical problems of drilling fluid technology is more prominent, including drill pipe wall is easy scaling, the annular clearance is too small, poor drilling fluid lubrication, large circulation resistance, poor carrying powder capacity, and high filtration, do not well in protected the hole wall and so on. Solving these problems need to improve drilling fluid performance. Through the establishment of the circulating pressure loss model derived:use lower penetration rate, strengthen the control of solid content, using clay free drilling fluid to control the drill pipe scaling; appropriate to increase the diameter of drill bit (raise the annular clearance 1mm, can reduce 0.5 times of the circulation pressure); Mixed with O-fluid lubricant in drilling fluid, PVA can reduced 0.6 times of lubrication coefficient; Mixed with PAC, XC and other good shear thinning properties of macromolecular polymers, PVA can improve the ratio of dynamic shear force of the drilling fluid and the capacity of portability powder; Mixed with SPNH and FT-1, PVA can reduce the filtration under 8ml.According to the Strata and the field drilling fluid of Luobusa in Tibet, PVA solid free drilling fluid was researched, which was low viscosity, low-cut, lubrication properties, strong inhibition ability and portable rock ability, with a shear thinning, and preferably resolve some of the issues in the drilling process, and ensure the drilling safe and improve drilling efficiency. Through a large number of field and laboratory experiments, PVA-clay free drilling fluid formulation is as follows:2.5%PVA 0.05%PAC 3%SPNH 0.5% O-lubricant. It has the following advantages:(1) Good rheology behavior:drilling fluid has low viscosity and low shear force, suitable core drilling small annular gap will help improve the penetration rate, reduced circulate resistance;(2) Significant effect of protection wall:compare with the usual low-solid mud by soaking experiment, after immersed in PVA-clay free drilling fluid 24h,the core is not deformation or expansion, and then put it into clear water 7d, it still no deformation, no collapse;(3) Excellent inhibitive ability:through the shale scrolling recovery test and expansion of high temperature and pressure experiments, summarized that PVA-clay free drilling fluid can be well suppressed high clay content, cementation loosed rock swelling and dispersion;(4) Small filtration and excellent lubrication:valchovite mainly used to decrease the filtration effect of drilling fluid, and plays a significant role; but it also more excellent in lubrication, and it has been able to meet the general requirements. When drilling deeper, larger circulate resistance, lubrication requirements need stronger, you can add O-type lubricant, it can significantly enhance the lubricating effect;(5) Good ability to carry meal:the drilling fluid through own development capacity of drilling fluid residue suspended test equipment, test PVA-clay free drilling fluid residue suspended effect is not better than low-solid mud, but on clay free drilling fluid terms, PVA-clay free drilling fluid has high ratio of dynamic shear force, can be better hanging row of diamond drill bit grinding down the rock powder, clean the bottom of the hole.