Demo, Sql Server - rextester

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CREATE TABLE Yourtable
    ([Order_strUserId] varchar(12), [Order_dtmInitiated] datetime, [Order_dtmLastUpdated] datetime)
;
    
INSERT INTO Yourtable
    ([Order_strUserId], [Order_dtmInitiated], [Order_dtmLastUpdated])
VALUES
    ('s2ir1f8vqx', '2016-12-13 15:06:17', '2016-12-13 15:06:59'),
    ('4839m6lnjchn', '2016-12-13 15:09:42', '2016-12-13 15:12:21'),
    ('y7k3u6q1wjn', '2016-12-13 15:11:40', '2016-12-13 15:12:01'),
    ('sdc74a0ahid', '2016-12-13 15:14:06', '2016-12-13 15:14:28'),
    ('2pgj2ixpta9', '2016-12-13 15:17:41', '2016-12-13 15:17:42'),
    ('qlfv4vmxdb', '2016-12-13 15:18:17', '2016-12-13 15:18:47'),
    ('y9jd24i59x5v', '2016-12-13 15:19:30', '2016-12-13 15:19:30'),
    ('9vb2d6u90hn', '2016-12-13 15:22:09', '2016-12-13 15:22:09')
	;

;WITH cte
		 AS (SELECT Min(Cast(Dateadd(minute, Datediff(minute, 0, Order_dtmInitiated), 0) AS SMALLDATETIME))   AS st_date,
					Max(Cast(Dateadd(minute, Datediff(minute, 0, Order_dtmLastUpdated), 0) AS SMALLDATETIME)) ed_date
			 FROM   Yourtable
			 UNION ALL
			 SELECT Dateadd(minute, 1, st_date),
					ed_date
			 FROM   cte
			 WHERE  st_date < ed_date)
	SELECT st_date,
		   Count(1)
	FROM   cte a
		   LEFT JOIN Yourtable b
				  ON a.st_date >= Cast(Dateadd(minute, Datediff(minute, 0, Order_dtmInitiated), 0) AS SMALLDATETIME)
					 AND a.st_date <= Cast(Dateadd(minute, Datediff(minute, 0, Order_dtmLastUpdated), 0) AS SMALLDATETIME)
	GROUP  BY st_date
	OPTION (maxrecursion 0)

View schema
Execution time: 0,03 sec, rows selected: 17, rows affected: 8, absolute service time: 0,17 sec