Hylseventilenhet, strömstyreanordning samt fremgangsmåte for stimulering av en underjordisk formasjon

A sleeve valve assembly for a downhole tool has a cylindrical housing (101) within which a sleeve valve member (114) is axially slidable within a radially expanded section (109) of the housing. The radially expanded section (109) of the housing presents an inwardly extending stop shoulder (110) at one point along its length and an annular expansion notch (112b) at another point. The sleeve valve member (114) includes a radially projecting chamfered boss (119) about its circumference. A portion of the sleeve valve is longitudinally slotted (117) so as to form collets (118). An outwardly biased C-ring (122) is disposed about the sleeve valve member (114) within the radially expanded section (109). The C-ring (122) is initially disposed to be free to travel axially along the radially expanded section between the boss (119) and the stop shoulder (110). As the sleeve valve is moved toward an open position, the boss (119), C-ring (122) and stop shoulder (110) engage each other such that the sleeve valve is releasably snagged against further axial movement toward the open position. A significant axial force upon the sleeve valve is required to effect unsnagging. Upon application of increased axial force, the collets (118) of the sliding sleeve member (114) are forced radially inward to permit the boss (119) to slip past the C-ring (122). A stimulation tool incorporating such a sleeve valve assembly is described which permits acid to be selectively communicated into the surrounding formation. A stimulation tool constructed in accordance with the present invention is particularly useful for acid stimulation applications in horizontal well conduits as the snagging feature of the sleeve valve assembly provides a positive indication that lateral acid flow ports within the shifter tool have been placed adjacent complementary flow ports in the surrounding housing.