Study On Damage Evaluation Method Of Cementing Cement Slurry Reservior

Cement reservoir protection is an important part of opening up the oil and gas reservoir drilling and drilling,and even the entire process of oil and gas field development.The problem of reservoir damage caused by cement slurry is directly related to the production of oil and gas wells,which is a problem that must be solved for the efficient and economic development of oil and gas reservoirs.The study on the evaluation method of cement slurry reservoir damage can be used to study the factors of cement reservoir damage,as well as its action mechanism and action law.Based on this,the theoretical basis and evaluation methods for the low-damage cement slurry system and the optimization of the cementing process are provided.Therefore,the evaluation method research is an important part of cement reservoir research.This article through a large number of literature,data research found that the current reservoir damage assessment device and evaluation methods have many deficiencies.In terms of evaluation devices,some devices lack the function of simulating the shape change of mud cakes in borehole walls.The specifications of some devices are only applicable to shallow wells.The structure of some devices is simple,and it is impossible to achieve multiple working fluids in sequence to damage the core and evaluate experimental results during drilling and completion.Some experimental devices cannot integrate damage and evaluation functions together.In terms of evaluation methods,there is a lack of cement slurry damage assessment methods for cement loss during cementing loss,and there is a lack of feasibility of laboratory filtrate infiltration depth calculation methods.Based on the characteristics and working conditions of reservoir damaged by cement slurry,the factors influencing the evaluation of reservoir damage are analyzed,and the technical requirements of the evaluation device are proposed.According to the research on the status quo at home and abroad and the requirements of the technical indicators of the device are evaluated,the device is developed.The main steps are:to make the theoretical model analysis device design feasibility;to design the overall structure and main functions of the device;to design each functional component;to process and debug the device.Through several improvements and perfections,a cement slurry reservoir damage simulator capable of real simulating high-temperature and high-pressure formation environments(temperature 200?,pressure difference 60 MPa),complete functions,miniaturization,and simple operation was developed.Considering cementing conditions,comparing various existing evaluation devices demonstrates the rationality of the device.Based on this device,an evaluation method for the damage of cement slurry reservoirs in line with the actual downhole conditions was established.In this paper,a new evaluation device and evaluation method are used to conduct field application research on the cement slurry reservoir damage evaluation method in a certain gas well.Experimental results:The permeability damage rate of conventional cement slurry reservoir in this block is 31.49%,with an average depth of 22.38cm.Loss of Cement Slurry Reservoir Damage by Cementing,Porosity Permeability Damage Percentage of 62.64%,Porosity-micro fracture core permeability damage rate of 87.62%.The evaluation results show that:For cementing operations with less risk of leakage,a low density and low water loss cement should be used,and the cement slurry filtrate should be compatible with the formation of clay minerals and formation water,drilling fluid filtrate compatibility;The cementing operation with increased leakage risk should adopt low density cement slurry,balanced pressure cementing and even pressure control cementing to avoid leakage.If the downhole condition is strictly restricted and the possibility of leakage is very great,the cement slurry system with acid dissolution and plugging is needed.