致密砂岩地层孕镶金刚石参数的试验优选研究

Experimental Optimization of Diamond Parameters for the Impregnated Diamond Bits Used in Tight Sandstone Formation

四川盆地须家河组致密砂岩地层研磨性强、可钻性差,采用常规高效牙轮和PDC钻头存在着钻头破岩效率差、单只钻头进尺少、机械钻速低等技术难题。首先设计了适用于孕镶金刚石钻头的钻凿特性测定试验装置,包括主体机架、钻进系统及岩样夹持系统等部分组成,能够针对孕镶金刚石钻头的破岩机理、磨损能力等进行分析。然后通过研制孕镶金刚石参数优选试验模拟钻头,采集须家河组致密砂岩地层的露头岩石,开展了模拟不同钻压、转速条件下金刚石粒度、浓度对孕镶钻头机械钻速和磨损量的影响试验。试验结果表明,随着金刚石粒度变小和浓度增大,有利于显著延长孕镶钻头的使用寿命;选用40/50目或50/60目金刚石粒度,同时配以70%左右的金刚石浓度,可以起到兼顾提高致密砂岩机械钻速和钻头寿命的效果,为今后四川盆地须家河组地层开展孕镶钻头的研制及应用提供了理论依据。

The tight sandstone in Xujiahe formation of Sichuan basin is competent with strong abrasivity and poor drillability,so if conventional tri-cone bits and PDC bits are adopted,some technical difficulties will emerge,such as poor rock breaking efficiency,short footage of single bit and low rate of penetration( ROP). To solve these difficulties,the drilling properties simulating equipment for the drilling tests of impregnated diamond bit was firstly developed. The simulating equipment is mainly composed of the rotary device, drilling system, rock clamping system,main frame and WOB simulation system,and it can be used to analyze the rock breaking mechanism and abrasive resistance of the impregnated diamond bit. Then,through developing the small bit for the experimental optimization of diamond parameters,mining the rock outcrops from the tight sandstone in Xujiahe formation,the experiments analyzing the effects of diamond granularity and concentration on impregnated diamond bit were carried out under the conditions of different WOB and rotary speed. The laboratory tests show that the diamond with smaller granularity and higher concentration is beneficial to significantly extend the life of impregnated diamond bit;and for the tight sandstone,the diamond with 40/50 or 50/60 mesh and70% concentration can improve both the drilling speed and the service life of impregnated diamond bit. It provides a theoretical basis for the development and application of impregnated diamond bits in Xujiahe formation of Sichuan basin.