Formation Damage Evaluation Of Exploratory Well At Dehui Block In Jilin

The tight gas reservoirs in Dehui area have low pressure coefficient and belong to sensitive gas reservoirs.The damage mechanism of Dehui area is studied.The results show that the clay minerals in Dehui area are mainly illite and chlorite.The core water phase trap injury rate is 40.67%~71.33%,with an average of 55.74%.The degree of closed injury is medium to strong.Using high temperature and high pressure dynamic damage device to simulate formation pore pressure,drilling fluid dynamic circulation pressure,cyclic shear rate and formation temperature during drilling,compare the permeability recovery value after dynamic damage of polymer drilling fluid system and oil-in-water drilling fluid system The results show that the oil-in-water drilling fluid system is easier to return to,the permeability recovery value after damage is higher,and the reservoir protection effect is better than the polymer drilling fluid system.Comparing the damage data under different pressure difference conditions,it can be seen that the permeability recovery value decreases continuously with the increase of the pressure difference.From the equilibrium state to the overbalanced state of 1 MPa,the permeability recovery value decreases the most.As time went on,the permeability recovery value continued to decrease;in the first 2 hours of damage,the permeability decreased the most.A mathematical model of the depth of penetration of the drilling fluid filtrate was established,which can provide reference for the design of the fluid loss performance of the drilling fluid.The numerical simulation software was used to simulate the intrusion process of the filtrate during the drilling process.It was found that the entire intrusion profile was inverted cone-shaped.Using the intrusion model established by the software,the influence of mud cake permeability and pressure difference on the intrusion depth was explored.The linear damage model and the radial damage model are established.By comparing the effects of linear damage and radial damage on productivity,it is found that when the depth of damage is the same,the impact of radial damage on well production is much greater than linear damage,and The more severe the decline in the permeability of the damaged zone,the greater the difference between the radial damage and the effect of linear damage on yield.