Calculating daily project drilling hours
I would consider first splitting the method into smaller methods as other people have mentioned.  The only suggestion for now is I might suggest changing your bool daily to a enumeration. This in theory means it might be easier to add a Hourly,Monthly etc reporting option.  Although this is only slightly better in my opinion and I'm sure there are better approaches  (maybe using interfaces?).

Something like this as an exercise in splitting things out into various methods keeping most of your code but just re-arranging it slightly.

public double CalculateDrillingHours(DrillingPeriod period = DrillingPeriod.Daily, bool timeFrame = false)
{
    Logger.Info("Calculating Drilling Hours");
    var tempList = GetDrillingTimes(period, timeFrame);

    var drillingHours = CalculateDrillingHours(tempList);
    SetDrillingTimes(period, drillingHours);

    return drillingHours;
}

private void SetDrillingTimes(DrillingPeriod period, double drillingHours)
{
    switch (period)
    {
        case DrillingPeriod.Daily:
            Logger.Info("Total Drilling Hours calculated");             
            DailyDrillingHours = drillingHours;
            break;
        case DrillingPeriod.Total:
            Logger.Info("Daily Drilling Hours calculated");
            TotalProjectDrillingHours = drillingHours;
            break;
        default:
            throw new NotImplementedException("Drilling period not supported");
    }
}

private List&lt;DateTime&gt; GetDrillingTimes(DrillingPeriod period, bool timeFrame)
{
    var query = "SELECT timestamp FROM myDatabase WHERE measured_dist = bit_loc AND rop &gt; 0";

    var daily = period == DrillingPeriod.Daily;
    query = BuildQuery(query, daily, timeFrame);

    var tempList = ExecuteQuery(query);

    if (tempList.Any())
    {
        return tempList;
    }

    // I would look at possibly using a custom exception here i.e. NoDataException
    throw new NoDataException("There was no data for the selected time frame.  Please select another. (Drilling Hours)");
} 

private double CalculateDrillingHours(List&lt;DateTime&gt; projectHours)
{
    return Convert.ToDouble(Math.Round(TimeCalculations(ConvertStringListToDateTimeList(projectHours)).TotalHours, 2, MidpointRounding.AwayFromZero));
}