Retention member for perforating guns
A perforating gun includes a charge tube having shaped charges affixed thereto. Each shaped charge includes a radially outward pointing post adapted to receive a detonator cord. A retention member installed on the post provides a compressive force that energetically couples the detonator cord to the post. The radially outermost portion of the retention member is radially flush with or radially recessed relative to the radially outermost portion of each post. In one embodiment, the retention member has a rounded medial portion, a central opening and a pair of locking tabs that point radially inward to the central opening. Each post may include a slot for receiving the detonator cord and a circumferential groove that is adapted to receive the locking tabs.
1. An apparatus for perforating a wellbore, comprising:
a charge tube;
a carrier tube having an interior bore in which the charge tube is disposed;
a plurality of shaped charges affixed in the charge tube, each shaped charge having a radially outward pointing post having a slot receiving a detonator cord having a circular cross-sectional profile; and
a retention member associated with each post, the retention member including an opening for receiving the post, wherein the retention member includes a medial curved bridge portion that conforms to the profile of the detonator cord, the bridge portion being circumferentially adjacent to the post such that it inhibits axial movement of the detonator cord, substantially all of the retention member being radially recessed relative to the radially outermost portion of the post.
2. The apparatus according to claim 1 , wherein the bridge portion includes a contour portion that conforms to a cross sectional shape of the detonator cord.
3. The apparatus according to claim 2 , wherein the bridge portion includes one of:
(i) two bridge portions;
(ii) a support member; and
(iii) a pair of fingers.
4. The apparatus according to claim 2 , wherein the bridge portion inhibits radial and axial movement of the detonator cord relative to the post.