Screened well drainage pipe structure with sealed, variable length labyrinth inlet flow control apparatus

摘要

A drainage pipe section for a horizontal subterranean well has a base pipe coaxially circumscribed by a tubular structure having a longitudinally intermediate portion defined by a sand screen assembly. An annular flow passage is formed between the base pipe and the tubular structure and communicates with the interior of the base pipe via base pipe sidewall openings positioned inwardly adjacent opposite end portions of the tubular structure. Annular adjustable flow control members having variable length labyrinth passages recessed into their outer sides are coaxially interposed in the annular flow passage between the opposite ends of the sand screen assembly and the base pipe sidewall openings. The flow control members are sealed within the annular flow passage by means of a rubber coating adhered to their outer side surfaces, and an adhesive type sealant material injected into annular spaces between the flow control members and facing portions of the base pipe. Specially designed plugs having resilient portions are used to selectively seal off portions of the labyrinth passage to selectively vary its effective length and thus the resistance to flow therethrough and the fluid flow into the base pipe interior through the annular flow passage. Additional seal structures are provided at the opposite ends of the tubular structure, each including a quantity of adhesive type resilient sealant material injected between the tubular structure end portion and the base pipe, and two annular resilient elastomeric backup seals.