Producing fluids from subterranean formations through lateral wells

Apparatus for drilling and completing a lateral wellbore from a primary wellbore, said apparatus comprising:

• a casing string adapted to be lowered in said primary wellbore;
• at least one pre-formed window unit in said casing string, said at least one pre-formed window unit comprising:
• an elongated housing having an inlet at its upper end and two outlets at its lower end,
• said inlet being fluidly connected to the lower end of that portion of said casing string which extends above said housing;
• a landing sub connected at one end to a first of said outlets and at its other end to the upper end of that portion of said casing string which extends below said housing, whereby said inlet, said first outlet, and said landing sub provide for continuous flow through said casing string;
• the other of said outlets providing a pre-formed window for drilling and completing said lateral wellbore from said primary wellbore wherein the longitudinal axis which extends through the center of said first outlet lies on or is substantially parallel to the longitudinal axis of said casing string while the longitudinal axis extending through the center of said second outlet forms a relatively small angle with respect to the longitudinal axis of said first outlet, said angle being equal to from about 1.degree. to about 10.degree..