Drilling and operating sigmoid-shaped wells

A method of drilling a hydrocarbon well, the method comprising:

• installing a wellhead system comprising disposing a wellhead body at a surface of the earth, the wellhead body comprising a wellhead passage configured to guide a drill string from a horizontal orientation to a downward sloping orientation of a wellbore having a sigmoid well trajectory, the wellhead passage comprising a conduit extending from a wellhead entrance at a vertically oriented side of the wellhead body to a wellhead exit at a horizontally oriented underside of the wellhead body;
• inserting a drill string into the wellhead passage, the drill string comprising a horizontally oriented starting end and a drill bit;
• and
• exerting a horizontal motive force on the horizontally oriented starting end of the drill string to generate a force to cause the drill bit to bore through the subsurface formation to create the wellbore having the sigmoid well trajectory, the wellbore comprising:
• a first sigmoid portion extending from the wellhead exit to an inflection point of the wellbore, the inflection point being located downhole from the wellhead exit, the first sigmoid portion of the wellbore comprising a first trajectory that is generally horizontal at the wellhead exit of the wellbore and that increases in slope to a first gradient at the inflection point;
• and
• a second sigmoid portion extending from the inflection point of the wellbore to a transition point of the wellbore, the transition point being located downhole from the inflection point, the second sigmoid portion of the wellbore comprising a second trajectory that matches the first gradient of the first sigmoid portion of the wellbore at the inflection point and that decreases in slope to a second gradient at the transition point.

A method comprising:

• installing a wellhead system comprising a wellhead passage comprising a conduit extending from a wellhead entry point in a vertically oriented side of a wellhead body of the wellhead system, to a wellhead exit point in a horizontally oriented underside of the wellhead body;
• and
• advancing a drill string through the wellhead passage to drill a horizontally-oriented hydrocarbon well comprising a sigmoid-shaped wellbore comprising an upper sigmoid portion comprising a downward curving wellbore trajectory and a lower sigmoid portion comprising an upward curving wellbore trajectory,
• the upper sigmoid portion comprising a first trajectory comprising a generally horizontal gradient at the wellhead exit point and that increases in downward gradient to a vertical gradient at an inflection point, and
• the lower sigmoid portion comprising a second trajectory that comprises the vertical gradient at the inflection point and decreases in downward gradient to a generally horizontal gradient at a horizontal transition point of the wellbore.