Apparatus and methods for measuring formation characteristics

摘要

An apparatus can measure characteristics of a formation surrounding a borehole. The apparatus comprises a tool body including a neutron measurement section including a neutron source and a neutron detector arrangement spaced in an axial direction from the neutron source; and
a density measurement section including a gamma ray source and a gamma ray detector arrangement spaced in an axial direction from the gamma ray source. The neutron measurement section and the density measurement section are positioned in the tool body so that the sections overlap in the axial direction and are azimuthally spaced apart in the tool body. The tool body also includes shielding to block a direct signal path from the neutron source to the gamma ray detector arrangement and to block a direct signal path from the gamma ray source to the neutron detector arrangement.