川西须家河组三段非均质性地层钻头研选及优化

Drill Bit Selection and Optimization of Heterogeneous Strata at Section 3 of Xujiahe Formation in Western Sichuan

川西须家河组气藏储层埋藏深、地质条件复杂、机械钻速低、钻井周期长、效益开发难度大,研选以6刀翼、16 mm平面齿和旋转齿为主的PDC钻头,在强化钻井参数条件下,钻头发生崩齿,导致提前磨损。建立须三段地应力分析模型,模拟地层骨架应力、井眼形状等对岩石可钻性的影响,认为须三段强非均质性地层首要考虑钻头的抗冲击性和耐磨性,其次是攻击性。据此开展钻头优选和优化改进,优化后的钻头具有双排布齿、力平衡设计、抗冲击性强的特点,并结合钻速敏感性影响因素分析,提出钻井参数“柔性”强化理念,根据钻遇岩性变化实时优化参数。通过钻头改进和钻井参数优化,平均单趟进尺增加1.6倍,出井正常磨损,基本解决须三段非均质地层的钻头崩齿和进尺短问题,表明该PDC钻头适合须三段钻进,为提高机械钻速,加快须家河组气藏开发提供了支撑。

There are several difficulties in gas reservoir of Xujiahe formation such as buried deeply,complex geological conditions,low rate of penetration,long drilling cycle etc.The PDC bit with 6 blades,16 mm plane teeth and rotary teeth is selected,but the bit teeth breaks and leads to premature wear under the condition of enhanced drilling parameters.A three-stage geostress analysis model is established to simulate the effects of formation skeleton stress and borehole shape on rock drillability.It is considered that the impact resistance and wear resistance of the drill bit should be considered first,followed by the aggression.Based on this,drill bit selection and improvement are carried out.The optimized bit has the characteristics of double-arranged teeth,force balance design and strong impact resistance.Combined with the analysis of influencing factors of drilling rate sensitivity,the strengthening concept of"flexibility"for drilling parameters is proposed,and the parameters are optimized in real time based on the changes of drilling lithology.Through the improvement of the bit and the optimization of drilling parameters,the average penetration of a single trip is increased by 1.6 times,and the wear out of well is normal,which basically solves the problems of bit breakage and short penetration in the three-stage heterogeneous strata.It shows that the PDC bit is suitable for three-stage drilling,and provides support for improving the mechanical drilling rate and accelerating the development of the second gas reservoir.