Systems and methods for heave compensation

A method implemented in a drilling system, comprising:

• receiving a plurality of block positions over time of a distance of a travelling block above a drill floor on a floating drill rig experiencing heave at a heave period of between 4 and 15 seconds, wherein:
• the plurality of block positions are associated with a depth of a bit in a wellbore;
• a measurement period of the plurality of block positions is approximately 1 Hz;
• and
• a measurement multiple of the measurement period to the heave period is between 4 and 15;
• applying a changepoint model to the plurality of block positions to separate the plurality of block positions into a plurality of segments by identifying a changepoint between different segments of the plurality of segments, and wherein at least two segments of the plurality of segments overlap a segment period, and wherein the at least two segments of the plurality of segments have different properties, the different properties including at least one of segment slope, segment length, function type, or fit, wherein the changepoint model identifies a de-sensitized block position of the plurality of block positions, wherein the de-sensitized block position is compensated for the heave by removing variability caused by the heave;
• using the de-sensitized block position, determining the depth of the bit and a rate of penetration of the bit, wherein the rate of penetration of the bit is compensated for the heave by removing the variability caused by the heave;
• based on the de-sensitized block position, the depth of the bit, and the rate of penetration of the bit, identifying a change in drilling conditions;
• and
• adjusting a drilling parameter based on the change in drilling conditions.

A drilling system, comprising:

• a processor and memory, the memory including instructions which cause the processor to:
• receive time-based block position data of a distance of a travelling block above a drill floor on a floating drill rig experiencing heave at a heave period of between 4 and 15 seconds, wherein:
• the time-based block position data is received from a block position sensor on the drill floor periodically with a measurement period of block position measurements of the time-based block position data;
• the measurement period is approximately 1 Hz;
• the time-based block position data is associated with a depth of a bit in a wellbore;
• and
• a measurement multiple of the measurement period to the heave period is between 4 and 15;
• apply a changepoint model to the time-based block position data to separate the time-based block position data into a plurality of segments by identifying a changepoint between different segments of the plurality of segments, and wherein at least two segments of the plurality of segments overlap a segment period, and wherein the at least two segments of the plurality of segments have different properties, the different properties including at least one of segment slope, segment length, function type, or fit;
• determine a best segment of the plurality of segments;
• generate a de-sensitized block position using the best segment of the plurality of segments, wherein the de-sensitized block position is compensated for the heave by removing variability caused by the heave;
• using the de-sensitized block position, determine the depth of the bit and a rate of penetration of the bit, wherein the rate of penetration of the bit is compensated for the heave by removing the variability caused by the heave;
• using the de-sensitized block position, the depth of the bit, and the rate of penetration of the bit, identify a change in drilling conditions at the bit;
• and
• adjust a drilling parameter based on the change in drilling conditions.