Preparation And Field Application Of Sodium Chloride Granule Diverting Agent

Petroleum and natural gas resources have always been an important strategic resource of a country,which is of great significance to the economic development and international status of a country and region.Over the years of oil well development,the comprehensive water cut of many old wells has risen seriously,and over 2/3 of the low permeability reservoirs in China have been proved.Therefore,increasing the development and utilization of low permeability reservoirs is an important direction to improve the reserves of oil and gas resources.For the difficult production of low permeability reservoirs,conventional repetitive fracturing technology is usually used to make the production potential of oil wells smaller and smaller in the later stage.It has become a new oil field production technology to plug new fractures or turn around by adding proppant into fractures.It has been recognized in old wells,water injection wells and some low permeability oil wells.As an important reagent for construction and production of low permeability reservoirs and heterogeneous formations,steering agent is widely used.In the process of construction and mining,it is necessary for the steering agent to have the following properties:a certain compressive strength,good plugging performance,soluble in water,so that it can be discharged back to the formation.At present,the commonly used steering agents have the following problems:weak compressive strength,high production cost,poor steering performance,small application scope,difficult plugging removal,great formation damage and environmental pollution.A new type of sodium chloride particle steering agent was prepared by using sodium chloride as raw material,water and hydrochloric acid as solvent,natural rubber and polymer as stabilizer and other auxiliaries.The raw material is easy to obtain,the preparation process is simple and easy to operate,and the amount of natural rubber and polymer used is small.Therefore,the product can solve many shortcomings of the existing steering agent.The idea of this study comes from the application of temporary plugging of calcium chloride particles.As a plugging particle used in early oil field stimulation,the damage to formation and reservoir is shown in the later stage.Therefore,sodium chloride particle fracturing diversion agent and acidizing diversion agent systems with good plugging performance,strong plugging removal ability,steering performance,green environmental protection and stability were prepared in the laboratory.NaCl was selected as raw material,NaCl and hydrochloric acid were selected according to the solid content of the steering agent;modified guar gum,xanthan gum and sodium polyacrylate were selected as stabilizers based on the salt resistance,acid resistance andstability of the polymer;corrosion inhibitors were determined as sodium molybdate and acid inhibitors based on the corrosion inhibition effect of the inhibitors at room temperature and high temperature;According to the dispersion and stability,SDS and sodium polyacrylate were selected as dispersants.The optimum mixing rate,droplet acceleration rate and feeding order were determined by studying the stabilization mechanism of steering agent.The final formulation of the sodium chloride particle fracturing diversion agent is 25 g NaCl+10 g CaCl2+10 g KCl+0.1%SDS(wt)+0.5%modified guar gum(wt)+0.1%sodium molybdate(wt).The stirring rate is 600 rpm.The final formulation of the acidification diversion agent is 54 g HCl(concentrated)+46 g water+8 g NaCl+0.1%sodium lignosulfonate(wt)+0.5%sodium polyacrylate(wt)+1.6%xanthan gum(wt)+1.5%acid with retarding agent.Corrosion agent(wt),stirring rate is 400 rpm,droplet acceleration rate of salt solution is controlled at 0.3-0.5 mL/s.Laboratory experiments prove that it has better steering performance,the plugging rate can reach more than 90%,the plugging removal rate can reach 80%,and the temperature resistance is general.It is possible to improve the temperature resistance by changing the solid content.One well was constructed separately,and both wells were successfully turned.The effect of two wells was obvious,and both wells made great breakthroughs in theory and technology.