The invention provides a method for measuring the
dryness of downhole steam in a
thermal recovery horizontal well, which comprises the steps of: forming a
capacitor by a two-phase mixed fluid of steam and water in a horizontal section in a mineshaft of the
thermal recovery horizontal well, a
capacitance sensor and a
capacitance probe, and measuring the
dryness of the steam in the horizontal section in the mineshaft of the
thermal recovery horizontal well. The water phase in the steam and water two-phase mixed fluid, the
capacitance sensor and the
capacitance probe form into a circular
capacitor, the water phase is taken as the negative
electrode of the circular
capacitor, the capacitance sensor and the
capacitance probe are taken as the positive
electrode of the circular capacitor, the capacitance sensor is used for measuring the
voltage and commutating the liquid level height of the water phase, and the relationship between the liquid level height of the water phase and the
voltage is as shown in the following formula so as to be capable obtaining the
dryness of the steam in the horizontal section in the mineshaft of the thermal
recovery horizontal well. The method has the characteristics of being extremely high in sensitivity to the water quantity, capable of measuring the downhole
water content of the thermal
recovery horizontal well, extremely high in sensitivity, small indryness measuring mean deviation which is less than 7%, convenient in application and operation and the like, thereby being widely applicable to the measurement technology of the dryness of the downhole steam in the oil thermal well.