Analysis Of Scaling Mechanism Of Wire-line Coring Drilling And Construction Of Flushing Fluid System

At present,wire-line coring technology has become the mainstream of drilling and coring technology at home and abroad,and has significant social and economic benefits.However,because of its small annulus space,a series of complex problems,such as hole wall stability,formation leakage and hole cleaning,are easily occurred during the circulation flow of the flushing fluid in the drill pipe.According to the actual project,this paper seeks the flushing liquid system suitable for wire-line coring drilling,so as to solve the scaling problem on the inner wall of drill pipe and realize the smooth fishing of core pipe.Based on the analysis of the scale sample,the scaling mechanism of the inner wall of the wire-line coring drill pipe is analyzed.Based on the investigation of relevant literature and the requirement of the performance of wire-line coring flushing fluid in field construction,a soilless weak gel flushing fluid system suitable for wire-line coring drilling is optimized and constructed,in the field application of ZK3901 in Zhaoyuan,Shandong Province,it can prevent the scaling on the inner wall of drill pipe in time.The main findings are as follows:(1)Through the analysis of the composition and particle size of the scale samples collected in the field,it can be concluded that the main composition of the scale is cuttings.And the particle size distribution of the scale sample combined with the calculation of the scale index can be known that in order to prevent the scaling on the inner wall of drill pipe,the particle size of solid particles in the washing fluid can be controlled to be less than 25.22?m.(2)Through the simulation of the flushing fluid circulating in the drill pipe,it is found that the discharge of the flushing fluid,the rotary speed of the drill pipe and the clearance of the drill pipe annulus have great influence on the flow pattern of the flushing fluid in the rope coring drilling,therefore,the stability of Hole Wall and the difficulty of scaling on the inner wall of drill pipe are affected.In addition,when the rotary speed of drill pipe is 360 r/min,the washing liquid has the greatest influence on the movement of solid particles.(3)Through laboratory research and evaluation,according to the characteristics of cordage drilling,the formula of the soilless weak GEL washing liquid system is:fresh water+0.1%Na OH+0.15%Na₂CO₃+0.3%xanthan gum+2.5%high temperature resistant starch+3%Ca CO₃+1.5%RHJ-1+5%KCL+0.2%fungicide,the temperature resistance of the system is100°C.When the content of xanthan gum was 0.6%,the temperature resistance of the system was 125°C.(4)Through laboratory study and evaluation,it is shown that the weak Gel wash solution has the following advantages:The use of biodegradable treatment agent material is friendly to the stratum ecosystem,the clay-free material,the solid particle size of the wash solution is small,the API filtrate loss is small(<6ml/30min),mud cake is thin and compact,Scaling Index is small(<1),YP/PV is big,carrying cuttings is strong,the solid particles that the washing liquid can suspend are big,the washing liquid further reduces the scaling probability of the drill pipe inner wall.(5)The soilless weak Gel solution has a good effect in field application.The mud cake formed by the flushing liquid is thin and compact,and solves the problem of slight and medium formation leakage.The Centrifugal machine is used to control the solid phase,the pump pressure is suitable,the inner wall of the drill pipe is rarely incrustation,and the drilling efficiency is good.