  Borehole gravity sensing can be used in a number of applications to measure
features around a well including rock-type change mapping and determination of
reservoir porosity. Quantum technology gravity sensors based on atom
interferometry have the ability to offer increased survey speeds and reduced
need for calibration. While surface sensors have been demonstrated in real
world environments, significant improvements in robustness and reductions to
radial size, weight, and power consumption are required for such devices to be
deployed in boreholes. To realise the first step towards the deployment of cold
atom-based sensors down boreholes, we demonstrate a borehole-deployable
magneto-optical trap, the core package of many cold atom-based systems. The
enclosure containing the magneto-optical trap itself had an outer radius of
($60\pm0.1$) mm at its widest point and a length of ($890\pm5$) mm. This system
was used to generate atom clouds at 1 m intervals in a 14 cm wide, 50 m deep
borehole, to simulate an in-borehole gravity surveys are performed. During the
survey the system generated on average clouds of (3.0 $\pm 0.1) \times 10^{5}$
$^{87}$Rb atoms with the standard deviation in atom number across the survey
observed to be as low as $9 \times 10^{4}$.
