钻井液暂堵剂颗粒粒径分布的最优化选择

Optimization of Particle Size Distribution for Temporarily Plugging/Shielding Agents in Water Base Reservoir Drilling Fluids

叙述了自1977年Abrams发表著名的'1/3架桥规则'以来,钻井液暂堵剂颗粒粒径选择技术的发展:罗平亚等人提出的使用3%刚性粒子+1.5%可变形粒子+1%～2%软化粒子的屏蔽暂堵技术(1992);屏蔽暂堵技术的分形理论处理和最优化;各种粒径连续分布理论及其物理实验方法和计算机模拟方法求解;理想充填理论和d 90规则.建立了暂堵剂颗粒粒径优化选择的图解法,开发了相应软件:实测、计算或估算储层最大孔径d 90;测绘颗粒累计体积分数～颗粒直径平方根关系曲线,以d90点与原点间连线为基线,取曲线从右方最接近基线的暂堵剂粒径分布为最优化粒径分布,再稍加大大粒径颗粒的比例,得到理想充填最优化粒径分布.基于某储层岩心的实测孔喉数据和各种商品碳酸钙粉的粒度组成数据,采用所建立的方法求得,用作该储层钻井液中暂堵剂的300目、600目、1000目碳酸钙粉的理想充填最优化质量比为60∶30∶10.经这种钻井液污染的储层岩心,渗透率恢复率高达82.9%,而传统屏蔽暂堵、1/3架桥规则及空白的钻井液污染后的储层岩心,渗透率恢复率分别为65.5%,44.1%,39.2%.图3表3参9.

The developments in choising particle size distribution (PSD) for temporarily plugging/shielding agents (TP/SAs) in water base reservoir drilling fluids (WBRDFs) since 1977, when Abrams published his famous“1/3 bridging rule”, are presented: concept and technology of temporarily plugging/shielding ( TP/S) by using 3% rigid + 1.5% deformable + 1—2% softening particles in WBRDFs ( Luo Ping-Ya et al, 1992 ); theoretical treatment and optimization of TP/S in terms of fractal geometry; various mathematical models for continuous PSD and ways of solving them through physical experiments and computer simulation; concept of ideal packing of particles andd90rule.A graphic method of optimizing PSD for TP/SAs and a soft ware for calculation are developed: to measure, caculate or estimate the maximal pore diameter,d90, of the aimed reservoir; to construct PSD curves cummulative volume fraction vz square foot diameter for every particulated material; to connect the original point and point (d90)1/2to give a baseline; to choose the PSD curve most closed to the baseline from the right side as optimized PSD and to reach the optimal PSD of ideal packing by increasing large sized particles a little more.By using this method suggested and on the base of the pore size data experimentally measured and of the particle size distribution for some grades of commercial powdered CaCO3, the optimizised and ideally packing mass ratio of powdered CaCO3grades of mesh 300,600, and 1000 is obtained as 60∶30∶10.For experimental reservoir cores poluted by the drilling fluids designed with this method, by classical TP/S technology, by 1/3 bridging rule, and blank, the permeability recovery rate is of 82.9%, 65.5%, 44.1%, and 39.2%, respectively.