STOCK-BASED COMPENSATION (Tables)

6 Months Ended

Mar. 31, 2022

Share-based Payment Arrangement [Abstract]

Schedule of Compensation Cost for Stock-Based Payment Arrangements

A summary of compensation cost for stock-based payment arrangements recognized in drilling services operating expense, research and development expense and selling, general and administrative expense on our Unaudited Condensed Consolidated Statements of Operations is as follows:

	Three Months Ended March 31,				Six Months Ended March 31,
(in thousands)	2022		2021		2022		2021
Stock-based compensation expense
Drilling services operating	$	1,282	$	1,529	$	2,522	$	3,292
Research and development	393		271		746		607
Selling, general and administrative	6,270		5,026		10,895		10,378
	$	7,945	$	6,826	$	14,163	$	14,277

Schedule of Restricted Stock Awards and Performance Share Units and Changes in Restricted Stock and Performance Share Units Outstanding

A summary of the status of our restricted stock awards as of March 31, 2022 and changes in non-vested restricted stock outstanding during the six months then ended is presented below:

(in thousands, except per share amounts)	Shares (1)	Weighted Average Grant Date Fair Value per Share
Non-vested restricted stock outstanding at September 30, 2021	1,412	$	37.36
Granted	744	25.83
Vested (2)	(602)	39.87
Forfeited	(38)	31.51
Non-vested restricted stock outstanding at March 31, 2022	1,516	$	30.86

(1)    Restricted stock shares include restricted phantom stock units under our Director Deferred Compensation Plan. These phantom stock units confer the economic benefits of owning company stock without the actual ownership, transfer or issuance of any shares. During the six months ended March 31, 2022, 14,199 restricted phantom stock units were granted and 18,906 restricted phantom stock units vested during the same period.

(2)    The number of restricted stock awards vested includes shares that we withheld on behalf of our employees to satisfy the statutory tax withholding requirements.

A summary of the status of our performance-vested restricted share units ("performance units") as of March 31, 2022 and changes in non-vested performance units outstanding during the six months ended is presented below:

(in thousands, except per share amounts)	Performance Units	Weighted Average Grant Date Fair Value per Performance Unit
Non-vested performance units outstanding at September 30, 2021	699	$	41.55
Granted	227	30.12
Vested (2)	(161)	62.66
Dividend equivalent right performance units credited	7	31.82
Forfeited	(46)	35.11
Non-vested performance units outstanding at March 31, 2022 (1)	726	$	33.68

(1)    Of the total non-vested performance units at the end of the period, specified performance criteria has been achieved with respect to 97,097 performance units which is calculated based on the payout percentage for the completed performance cycle. The vesting and number of the remainder of non-vested performance units reflected at the end of the period is contingent upon our achievement of specified target performance criteria. If we meet the specified maximum performance criteria, approximately 910,492 additional performance units could vest or become eligible to vest.

(2)    The number of performance units vested includes units that we withheld on behalf of our employees to satisfy the statutory tax withholding requirements.