this brought the total u.s. rig count to 929 , at december 31 , 2017 , an increase of 41 % during 2017 compared to 659 rigs at the end of the 2016. given the historical volatility of crude prices , there is a continued risk that if prices do not continue to improve , or if they start to decline again due to high levels of crude oil production , there is a potential for slowing growth rates in various global regions and or for ongoing supply/demand imbalances . prices for natural gas in the u.s. averaged $ 2.99 per mmbtu for 2017 , compared to $ 2.40 per mmbtu for 2016. as a result of natural gas production growth outpacing demand in the u.s. , natural gas prices continue to be weak relative to prices experienced from 2006 through 2008 and are expected to remain below levels considered economical for new investments in numerous natural gas fields . draws in late 2017 were larger than normal , resulting in total u.s. natural gas inventories of 2.8 trillion cubic feet at the end of 2017 , 13.0 % lower than levels at this time a year ago , and 12.1 % lower than the five-year average . inventories are expected to build slightly above the five year average by the end of october 2018. after a period of growth in exploration activities and associated spending leading up to the end of 2014 , many e & p companies shifted their focus to production activities , away from exploration , as the continued decline in oil and gas prices resulted in decreased revenues , prompting cost reduction initiatives across the industry . from the end of 2014 through 2017 , e & p companies decreased spending on exploration and reportedly focused their spending on critical production requirements and existing commitments . we believe this was due to several factors , but primarily because operational cash flows of e & p companies were no longer sufficient to cover capital expenditures while continuing to pay cash dividends to shareholders . e & p companies relied on asset sales and debt financings to fund capital requirements amid demands for greater returns to shareholders . the combination of these factors placed many e & p companies in a position where they were unable to cover both their capital expenditure budgets and targeted cash returns to shareholders . as a result , e & p companies dramatically cut spending , with exploration spending receiving the largest reductions and seismic spending being one of the most discretionary parts of their exploration budgets . as a result of this industry downturn , many customers experienced a significant reduction in their liquidity with challenges accessing the capital markets . several exploration and production companies declared bankruptcy , or exchanged equity for the forgiveness of debt , while others were forced to sell assets in an effort to preserve 34 liquidity . however , over the past 12 months , access to the capital and debt markets improved significantly for certain of these customers . e & p spending is expected to continue to rebound in 2018 over 2017 , which was preceded by two successive years of double digit declines as commodity prices are forecasted to remain more stable . this positive trend in e & p spending , aided by favorable macroeconomic conditions has resulted in increased revenues during 2017. if the global supply of oil decreases due to reduced capital investment by e & p companies , government instability occurs in a major oil-producing nation or energy demand increases in the u.s. or in countries such as china and india , the recovery in wti and brent crude oil prices could continue to improve . if commodity prices do not continue to improve or if they start to deteriorate again , demand for our services and products could decline . impact to our business during 2017 , we saw renewed customer interest in underwriting of our new venture multi-client programs as oil companies were able to right-size their expenditures to current oil prices and generate profits for the first time in eight quarters . during 2017 , revenues increased 14 % versus prior year . investments in our multi-client data library are dependent upon the timing of our new venture projects and the availability of underwriting by our customers . we continue to maintain high standards for the underwriting of any new projects , and sanctioned several new programs during 2017 that were originally planned to occur during 2016. our “ asset light ” strategy enables us to scale our business to avoid significant fixed costs and to remain financially flexible as we manage the timing and levels of our capital expenditures . in our e & p technology & services segment , our new venture revenues increased driven by our 3-d multi-client reimaging programs offshore mexico and brazil , as well as revenues from a new 2-d multi-client program in panama and other programs that have recently been launched , which met our conservative underwriting standards . imaging services revenues decreased as a result of our strategic shift toward higher return multi-client programs . the imaging work on multi-client programs are reflected as part of new venture or data library revenues depending on the program status , whereas revenues from proprietary imaging programs are reflected as part of imaging services . the imaging services group is fully utilized , with a large portion of our capacity dedicated to multi-client programs . story_separator_special_tag other income — other income for 2016 was $ 1.4 million compared to other income of $ 98.3 million for 2015. the difference primarily relates to changes in our accrual for loss contingency related to a legal matter . see further discussion at footnote 6 “ legal matters ” and in part 1 , item 3 , “ legal proceedings . ” the following table reflects the significant items of other income ( in thousands ) : replace_table_token_9_th income tax expense — income tax expense for 2016 was $ 4.4 million compared to $ 4.0 million for 2015. our effective tax rates for 2016 and 2015 were ( 7.3 ) % and ( 19.2 ) % , respectively . our effective tax rate for 2016 and 2015 was negatively impacted by the establishment of a valuation allowance related to our u.s. losses incurred in both years . see further discussion of establishment of the deferred tax valuation allowance at footnote 5 “ income taxes ” of footnotes to consolidated financial statements . our income tax expense for 2016 and 2015 relates to income from our non-u.s. businesses . this foreign tax expense has not been offset by the tax benefits on losses within the u.s. and other jurisdictions , from which we can not currently benefit . liquidity and capital resources sources of capital as of december 31 , 2017 , we had $ 52.1 million in cash on hand and $ 15.5 million of undrawn borrowing base availability under the credit facility . our cash requirements include working capital requirements and cash required for our debt service payments , multi-client seismic data acquisition activities and capital expenditures . as of december 31 , 2017 , we had working capital of $ ( 8.6 ) million , which includes a current liability of $ 28.5 million of senior secured third-priority lien notes that are payable during the second quarter of 2018 , which we expect to pay using available liquidity . working capital requirements are primarily driven by our investment in our ( i ) multi-client data library ( $ 23.7 million in 2017 ) and royalty payments for multi-client sales . also , our headcount has traditionally been a significant driver of our working capital needs . as a significant portion of our business is involved in the planning , processing and interpretation of seismic data , one of our largest investments is in our employees , which involves cash expenditures for their salaries , bonuses , payroll taxes and related compensation expenses . during late 2014 and continuing through mid-2016 , we reduced our workforce by over 60 % , and closed selected facilities . our workforce has since stabilized . these actions are expected to result in annualized cash savings of approximately $ 95 million which we began to fully realize in 2017. during 2017 , we saw an improved operating environment in oil prices which has contributed to a stabilization in our workforce . 42 our working capital requirements may change from time to time depending upon many factors , including our operating results and adjustments in our operating plan in response to industry conditions , competition and unexpected events . in recent years , our primary sources of funds have been cash flows generated from operations , existing cash balances , debt and equity issuances and borrowings under our revolving credit facilities . revolving credit facility in august 2014 , we and our material u.s. subsidiaries , gx technology corporation , ion exploration products ( u.s.a. ) , inc. and i/o marine systems , inc. ( collectively , the “ subsidiary borrowers ” ) entered into a revolving credit and security agreement with pnc bank , national association ( “ pnc ” ) , as agent ( the “ original credit agreement ” ) , which was amended by the first amendment to revolving credit and security agreement in august 2015 ( the “ first amendment ” ) and the second amendment to revolving credit and security agreement in april 2016 ( the “ second amendment ” ; the original credit agreement , as amended by the first amendment and the second amendment , the “ credit facility ” ) . the credit facility is available to provide for the borrowers ' general corporate needs , including working capital requirements , capital expenditures , surety deposits and acquisition financing . the maximum amount of the revolving line of credit under the credit facility is the lesser of $ 40.0 million and a monthly borrowing base ( which may be recalculated more frequently under certain circumstances ) . the borrowing base under the credit facility will increase or decrease monthly using a formula based on certain eligible receivables , eligible inventory and other amounts , including a percentage of the net orderly liquidation value of our multi-client data library ( not to exceed $ 15.0 million for the multi-client data library data component ) . as of december 31 , 2017 , the borrowing base under the credit facility was $ 25.5 million , and there was $ 10.0 million of outstanding indebtedness under the credit facility . we experienced a significant increase in our accounts and unbilled receivables during the second half of 2017 due to the significant revenue increase , however , a majority of those increases were part of our foreign operations , which are not included in the borrowing base calculation . the credit facility requires us to maintain compliance with various covenants . at december 31 , 2017 , we were in compliance with all of the covenants under the credit facility . for further information regarding our credit facility see footnote 3 “ long-term debt and lease obligations ” of footnotes to consolidated financial statements . senior secured notes in may 2013 , we sold $ 175.0 million aggregate principal amount of 8.125 % senior secured second-priority notes due 2018 ( the “ third lien notes ” ) in a

cash flow from operations net cash provided by operating activities was $ 28.0 million for 2017 , compared to net cash used in operating activities of $ 1.6 million for 2016 . the increase in net cash provided by operations was due to a significant increase in new venture revenues in 2017 , compared to 2016 and due to $ 20.8 million damages payment in 2016 for the westerngeco lawsuit , which was partially offset by increases in unbilled receivables as of december 31 , 2017. net cash provided by operating activities was $ 1.6 million for 2016 , compared to net cash used in operating activities of $ 16.5 million for 2015. the increase in our cash flows from operations was primarily due to reduced spend due to our cost reduction initiatives and accounts receivable collections offset by a $ 20.8 million damages payment for the westerngeco lawsuit . cash flow used in investing activities net cash flow used in investing activities was $ 24.8 million for 2017 , compared to $ 13.6 million for 2016 . the principal uses of cash in our investing activities during 2017 were $ 23.7 million of investments in our multi-client data library and $ 1.1 million of investments in property , plant and equipment . 44 net cash flow used in investing activities was $ 13.6 million for 2016 , compared to $ 63.5 million for 2015. the principal uses of cash in our investing activities during 2016 were $ 14.9 million of investments in our multi-client data library and $ 1.5 million of investments in property , plant and equipment , partially offset by proceeds from the escrow related to the sale of a cost method investment in 2014. cash flow used in financing activities net cash flow used in financing activities was $ 3.6 million for 2017 , compared to $ 21.6 million of net cash flow used in financing activities for 2016 .


 Write a concise suspicious activity report of the following text delimited by triple backquotes. Return your response as a formal report which covers the key points highlighting the location,dates,entity names and account holder information in chronological order of the text.
     ```cash flow from operations net cash provided by operating activities was $ 28.0 million for 2017 , compared to net cash used in operating activities of $ 1.6 million for 2016 . the increase in net cash provided by operations was due to a significant increase in new venture revenues in 2017 , compared to 2016 and due to $ 20.8 million damages payment in 2016 for the westerngeco lawsuit , which was partially offset by increases in unbilled receivables as of december 31 , 2017. net cash provided by operating activities was $ 1.6 million for 2016 , compared to net cash used in operating activities of $ 16.5 million for 2015. the increase in our cash flows from operations was primarily due to reduced spend due to our cost reduction initiatives and accounts receivable collections offset by a $ 20.8 million damages payment for the westerngeco lawsuit . cash flow used in investing activities net cash flow used in investing activities was $ 24.8 million for 2017 , compared to $ 13.6 million for 2016 . the principal uses of cash in our investing activities during 2017 were $ 23.7 million of investments in our multi-client data library and $ 1.1 million of investments in property , plant and equipment . 44 net cash flow used in investing activities was $ 13.6 million for 2016 , compared to $ 63.5 million for 2015. the principal uses of cash in our investing activities during 2016 were $ 14.9 million of investments in our multi-client data library and $ 1.5 million of investments in property , plant and equipment , partially offset by proceeds from the escrow related to the sale of a cost method investment in 2014. cash flow used in financing activities net cash flow used in financing activities was $ 3.6 million for 2017 , compared to $ 21.6 million of net cash flow used in financing activities for 2016 .
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 Suspicious Activity Report : this brought the total u.s. rig count to 929 , at december 31 , 2017 , an increase of 41 % during 2017 compared to 659 rigs at the end of the 2016. given the historical volatility of crude prices , there is a continued risk that if prices do not continue to improve , or if they start to decline again due to high levels of crude oil production , there is a potential for slowing growth rates in various global regions and or for ongoing supply/demand imbalances . prices for natural gas in the u.s. averaged $ 2.99 per mmbtu for 2017 , compared to $ 2.40 per mmbtu for 2016. as a result of natural gas production growth outpacing demand in the u.s. , natural gas prices continue to be weak relative to prices experienced from 2006 through 2008 and are expected to remain below levels considered economical for new investments in numerous natural gas fields . draws in late 2017 were larger than normal , resulting in total u.s. natural gas inventories of 2.8 trillion cubic feet at the end of 2017 , 13.0 % lower than levels at this time a year ago , and 12.1 % lower than the five-year average . inventories are expected to build slightly above the five year average by the end of october 2018. after a period of growth in exploration activities and associated spending leading up to the end of 2014 , many e & p companies shifted their focus to production activities , away from exploration , as the continued decline in oil and gas prices resulted in decreased revenues , prompting cost reduction initiatives across the industry . from the end of 2014 through 2017 , e & p companies decreased spending on exploration and reportedly focused their spending on critical production requirements and existing commitments . we believe this was due to several factors , but primarily because operational cash flows of e & p companies were no longer sufficient to cover capital expenditures while continuing to pay cash dividends to shareholders . e & p companies relied on asset sales and debt financings to fund capital requirements amid demands for greater returns to shareholders . the combination of these factors placed many e & p companies in a position where they were unable to cover both their capital expenditure budgets and targeted cash returns to shareholders . as a result , e & p companies dramatically cut spending , with exploration spending receiving the largest reductions and seismic spending being one of the most discretionary parts of their exploration budgets . as a result of this industry downturn , many customers experienced a significant reduction in their liquidity with challenges accessing the capital markets . several exploration and production companies declared bankruptcy , or exchanged equity for the forgiveness of debt , while others were forced to sell assets in an effort to preserve 34 liquidity . however , over the past 12 months , access to the capital and debt markets improved significantly for certain of these customers . e & p spending is expected to continue to rebound in 2018 over 2017 , which was preceded by two successive years of double digit declines as commodity prices are forecasted to remain more stable . this positive trend in e & p spending , aided by favorable macroeconomic conditions has resulted in increased revenues during 2017. if the global supply of oil decreases due to reduced capital investment by e & p companies , government instability occurs in a major oil-producing nation or energy demand increases in the u.s. or in countries such as china and india , the recovery in wti and brent crude oil prices could continue to improve . if commodity prices do not continue to improve or if they start to deteriorate again , demand for our services and products could decline . impact to our business during 2017 , we saw renewed customer interest in underwriting of our new venture multi-client programs as oil companies were able to right-size their expenditures to current oil prices and generate profits for the first time in eight quarters . during 2017 , revenues increased 14 % versus prior year . investments in our multi-client data library are dependent upon the timing of our new venture projects and the availability of underwriting by our customers . we continue to maintain high standards for the underwriting of any new projects , and sanctioned several new programs during 2017 that were originally planned to occur during 2016. our “ asset light ” strategy enables us to scale our business to avoid significant fixed costs and to remain financially flexible as we manage the timing and levels of our capital expenditures . in our e & p technology & services segment , our new venture revenues increased driven by our 3-d multi-client reimaging programs offshore mexico and brazil , as well as revenues from a new 2-d multi-client program in panama and other programs that have recently been launched , which met our conservative underwriting standards . imaging services revenues decreased as a result of our strategic shift toward higher return multi-client programs . the imaging work on multi-client programs are reflected as part of new venture or data library revenues depending on the program status , whereas revenues from proprietary imaging programs are reflected as part of imaging services . the imaging services group is fully utilized , with a large portion of our capacity dedicated to multi-client programs . story_separator_special_tag other income — other income for 2016 was $ 1.4 million compared to other income of $ 98.3 million for 2015. the difference primarily relates to changes in our accrual for loss contingency related to a legal matter . see further discussion at footnote 6 “ legal matters ” and in part 1 , item 3 , “ legal proceedings . ” the following table reflects the significant items of other income ( in thousands ) : replace_table_token_9_th income tax expense — income tax expense for 2016 was $ 4.4 million compared to $ 4.0 million for 2015. our effective tax rates for 2016 and 2015 were ( 7.3 ) % and ( 19.2 ) % , respectively . our effective tax rate for 2016 and 2015 was negatively impacted by the establishment of a valuation allowance related to our u.s. losses incurred in both years . see further discussion of establishment of the deferred tax valuation allowance at footnote 5 “ income taxes ” of footnotes to consolidated financial statements . our income tax expense for 2016 and 2015 relates to income from our non-u.s. businesses . this foreign tax expense has not been offset by the tax benefits on losses within the u.s. and other jurisdictions , from which we can not currently benefit . liquidity and capital resources sources of capital as of december 31 , 2017 , we had $ 52.1 million in cash on hand and $ 15.5 million of undrawn borrowing base availability under the credit facility . our cash requirements include working capital requirements and cash required for our debt service payments , multi-client seismic data acquisition activities and capital expenditures . as of december 31 , 2017 , we had working capital of $ ( 8.6 ) million , which includes a current liability of $ 28.5 million of senior secured third-priority lien notes that are payable during the second quarter of 2018 , which we expect to pay using available liquidity . working capital requirements are primarily driven by our investment in our ( i ) multi-client data library ( $ 23.7 million in 2017 ) and royalty payments for multi-client sales . also , our headcount has traditionally been a significant driver of our working capital needs . as a significant portion of our business is involved in the planning , processing and interpretation of seismic data , one of our largest investments is in our employees , which involves cash expenditures for their salaries , bonuses , payroll taxes and related compensation expenses . during late 2014 and continuing through mid-2016 , we reduced our workforce by over 60 % , and closed selected facilities . our workforce has since stabilized . these actions are expected to result in annualized cash savings of approximately $ 95 million which we began to fully realize in 2017. during 2017 , we saw an improved operating environment in oil prices which has contributed to a stabilization in our workforce . 42 our working capital requirements may change from time to time depending upon many factors , including our operating results and adjustments in our operating plan in response to industry conditions , competition and unexpected events . in recent years , our primary sources of funds have been cash flows generated from operations , existing cash balances , debt and equity issuances and borrowings under our revolving credit facilities . revolving credit facility in august 2014 , we and our material u.s. subsidiaries , gx technology corporation , ion exploration products ( u.s.a. ) , inc. and i/o marine systems , inc. ( collectively , the “ subsidiary borrowers ” ) entered into a revolving credit and security agreement with pnc bank , national association ( “ pnc ” ) , as agent ( the “ original credit agreement ” ) , which was amended by the first amendment to revolving credit and security agreement in august 2015 ( the “ first amendment ” ) and the second amendment to revolving credit and security agreement in april 2016 ( the “ second amendment ” ; the original credit agreement , as amended by the first amendment and the second amendment , the “ credit facility ” ) . the credit facility is available to provide for the borrowers ' general corporate needs , including working capital requirements , capital expenditures , surety deposits and acquisition financing . the maximum amount of the revolving line of credit under the credit facility is the lesser of $ 40.0 million and a monthly borrowing base ( which may be recalculated more frequently under certain circumstances ) . the borrowing base under the credit facility will increase or decrease monthly using a formula based on certain eligible receivables , eligible inventory and other amounts , including a percentage of the net orderly liquidation value of our multi-client data library ( not to exceed $ 15.0 million for the multi-client data library data component ) . as of december 31 , 2017 , the borrowing base under the credit facility was $ 25.5 million , and there was $ 10.0 million of outstanding indebtedness under the credit facility . we experienced a significant increase in our accounts and unbilled receivables during the second half of 2017 due to the significant revenue increase , however , a majority of those increases were part of our foreign operations , which are not included in the borrowing base calculation . the credit facility requires us to maintain compliance with various covenants . at december 31 , 2017 , we were in compliance with all of the covenants under the credit facility . for further information regarding our credit facility see footnote 3 “ long-term debt and lease obligations ” of footnotes to consolidated financial statements . senior secured notes in may 2013 , we sold $ 175.0 million aggregate principal amount of 8.125 % senior secured second-priority notes due 2018 ( the “ third lien notes ” ) in a

