Experimental Study On A New Uniform Acidizing Process

In heterogeneous reservoirs,conventional acidizing techniques typically result in a non-uniform distribution of acid in the reservoir.This is because the acid liquid preferentially enters the high-permeability layer after entering the reservoir,and the low-permeability layer that needs to be stimulated rarely enters the acid,resulting in a poor acidizing reconstruction effect.The existing uniform acidizing technology is mainly composed of two major categories:mechanical method and chemical method,the former generally has problems of complicated operation,high cost,and many restrictions on use;the latter has many problems such as small plugging pressure,incomplete plugging and unfriendly to the reservoir.In this paper,a new type of uniform acidizing process is proposed.In the acidification process,in which a new type of temporary plugging diverting agent(smart diverting agent)is pumped into the formation.Its greatest feature is the use of continuous temperature rising of the formation to achieve intelligent transformation process of "Liquid-Gel-Liquid".The ground condition of the smart diverting agent is liquid,after pumping into the formation,it first flows into the high-permeability layer.Under the stimulation of temperature,liquid changed to gel phase to plugging the high permeability layer,and the acid naturally flows into the low permeability layer.The uniform acidification of heterogeneous formations in long wellbore section is eventually realized by alternating multi-stage injection of acid and smart diverting agent.And as the temperature continue rising,the smart diverting agent(gel phase)that plugs the high permeability can completely break into liquid and return it along with the residual acid.The whole process of uniform acidizing is simple and convenient,and has zero pollution to the formation.The main research contents of this paper are follows:(1)Based on the theory of supramolecular chemistry and hydrogel chemistry,the two systems of organogel and hydrogel were developed,and the SA-D system smart diverting agent with good gel-forming and gel-breaking ability was selected.The gelation and gel-breaking mechanism of the agent were studied.The results show that the Schiff base reaction is the precondition for the gelation.The high temperature makes the ether linkage break apart is the real cause of the gel breaking.The smart diverting agent can control the gelation and gel breaking time by adjusting the concentration of the crosslinking unit,and it has a strong acid resistance.(2)Uniform acidizing physics simulation experiments were carried out under laboratory conditions,the single core plugging experiment found that there is a binomial function relationship between the compressive strength of the smart diverting agent's plugging radius and the high temperature plugging removal effect is excellent.The results of the shunt acidification experiment of the parallel core show that the smart diverting agent has a good temporary blocking and diverting effect.(3)Taking an actual well as an example,the oilfield application effect analysis of the new uniform acidizing process was carried out,and the control parameters required for the field application of the new uniform acidizing process are optimized like the amount and displacement of the smart diverting agent.The results show that after injecting the smart diverting agent,the pressure increased by 3 MPa,indicating that the smart diverting agent has a certain degree of plugging effect on the high-permeability layer.The pressure of the subsequent acid injection is slightly reduced,indicating that the acid liquid enters the low-permeability layer and begins to remove plugging,which verified the effectiveness of the uniform acidizing process.In this paper,a new uniform acidizing process was proposed by means of material development,physical simulation of uniform acidizing and field application.The smart diverting agent used in this uniform acidizing process has excellent performance,and the application of uniform acidizing in the field is obvious.It has a good application prospect in the uniform acidizing operation of heterogeneous reservoirs.