STOCK-BASED COMPENSATION (Tables)

3 Months Ended

Dec. 31, 2020

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 during the three months ended December 31, 2020 and 2019 is as follows:

	Three Months Ended December 31,
(in thousands)	2020		2019
Stock-based compensation expense
Stock options	$	318	$	571
Restricted stock	6,011		7,370
Performance share units	1,122		2,260
	$	7,451	$	10,201

Schedule of Stock Option Activity

A summary of stock option activity under all existing long-term incentive plans for the three months ended December 31, 2020 is presented in the following table:

(in thousands, except per share amounts and years)	Shares	Weighted Average Exercise Price		Weighted Average Remaining Contractual Term in Years	Aggregate Intrinsic Value
Outstanding at September 30, 2020	2,863	$	62.41
Exercised	—	—
Forfeited/Expired	(174)	48.17
Outstanding at December 31, 2020	2,689	$	63.34	4.54	$	—
Vested or expected to vest at December 31, 2020	158	$	59.28	6.93	$	—
Exercisable at December 31, 2020	2,531	$	63.59	4.39	$	—

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 December 31, 2020 and changes in non-vested restricted stock outstanding during the three 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, 2020	1,280	$	49.81
Granted	631	25.29
Vested (2)	(466)	55.93
Forfeited	(2)	49.07
Non-vested restricted stock outstanding at December 31, 2020	1,443	$	37.08

(1)    The beginning balance of restricted stock shares includes phantom shares that confer the benefits of owning company stock without the actual ownership or transfer of any shares. There were no phantom shares granted during the three months ended December 31, 2020. There were 20,616 phantom shares granted during fiscal year 2020.

(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 share units as of December 31, 2020 and changes in non-vested performance share units outstanding during the three months then ended is presented below:

(in thousands, except per share amounts)	Shares	Weighted Average Grant Date Fair Value per Share
Non-vested performance share units outstanding at September 30, 2020	337	$	51.09
Granted	313	29.77
Reinvested dividends	42	52.85
Non-vested performance share units outstanding at December 31, 2020	692	$	41.58

Schedule of Weighted-Average Assumptions Used in the Calculation of the Fair Value of Awards

The weighted-average fair value calculation for performance share units granted during the three months ended December 31, 2020 is based on the following weighted-average assumptions set forth in the table below.

	Three Months Ended December 31, 2020
Risk-free interest rate (1)	0.2	%
Expected stock volatility (2)	62.3	%
Expected term (in years)	3.1

(1)The risk-free interest rate is based on U.S. Treasury securities for the expected term of the performance share units.

(2)Expected volatilities are based on the daily closing price of our stock based upon historical experience over a period which approximates the expected term of the performance share units.