Surface transit time determination

A non-transitory computer-readable medium storing instructions that, when executed by at least one processor of a computing system, cause the computing system to perform operations, the operations comprising:

• receiving an outlet drilling fluid parameter measured by an outlet sensor, wherein the outlet drilling fluid parameter comprises a level or a flow rate of a drilling fluid, and wherein the outlet sensor is positioned downstream from an outlet of a wellbore;
• determining a first time when the outlet drilling fluid parameter increases by more than a predetermined outlet drilling fluid parameter threshold;
• receiving an inlet drilling fluid parameter measured by an inlet sensor, wherein the inlet drilling fluid parameter comprises the level or the flow rate, and wherein the inlet sensor is positioned downstream from the outlet sensor and upstream from an inlet of the wellbore;
• determining a second time when the inlet drilling fluid parameter becomes substantially constant or increases by more than a predetermined inlet drilling fluid parameter threshold;
• determining a surface transit time of the drilling fluid by subtracting the first time from the second time;
• determining an outlet hydrocarbon contribution in the drilling fluid based at least partially upon gas extracted from the drilling fluid by a gas extractor, wherein the gas extractor is positioned at the outlet of the wellbore, at a shaker, or between the outlet of the wellbore and the shaker;
• and
• determining an inlet hydrocarbon contribution in the drilling fluid based at least partially upon the surface transit time and the outlet hydrocarbon contribution.

A computing system, comprising:

• one or more processors;
• and
• a memory system comprising one or more non-transitory computer-readable media storing instructions that, when executed by at least one of the one or more processors, cause the computing system to perform operations, the operations comprising:
• receiving an outlet drilling fluid parameter measured by an outlet sensor, wherein the outlet drilling fluid parameter comprises a level or a flow rate of a drilling fluid, and wherein the outlet sensor comprises:
• a first level sensor configured to measure the level of the drilling fluid in a shaker, wherein the shaker is positioned downstream from an outlet of a wellbore and upstream from an inlet sensor;
• or
• a first flow paddle configured to measure the flow rate of the drilling fluid through the outlet of the wellbore, through the shaker, or between the outlet of the wellbore and the shaker;
• determining a first time when the outlet drilling fluid parameter increases by more than a predetermined outlet drilling fluid parameter threshold;
• receiving an inlet drilling fluid parameter measured by the inlet sensor, wherein the inlet drilling fluid parameter comprises the level or the flow rate, and wherein the inlet sensor comprises:
• a second level sensor configured to measure the level of the drilling fluid in a suction tank, wherein the suction tank is positioned downstream from the shaker and upstream from an inlet of the wellbore;
• or
• a second flow paddle configured to measure the flow rate of the drilling fluid into the suction tank, into the inlet of the wellbore, or between the suction tank and the inlet of the wellbore;
• determining a second time when the inlet drilling fluid parameter becomes substantially constant or increases by more than a predetermined inlet drilling fluid parameter threshold;
• determining a surface transit time of the drilling fluid by subtracting the first time from the second time;
• determining an outlet hydrocarbon contribution in the drilling fluid based at least partially upon gas extracted from the drilling fluid by an outlet gas extractor, wherein the outlet gas extractor is positioned at the outlet of the wellbore, at the shaker, or between the outlet of the wellbore and the shaker;
• determining an inlet hydrocarbon contribution in the drilling fluid based at least partially upon the surface transit time and the outlet hydrocarbon contribution;
• and
• determining an actual hydrocarbon contribution in the drilling fluid from a subterranean formation by subtracting the inlet hydrocarbon contribution from the outlet hydrocarbon contribution.