Interest expense. Interest expense for the three months ended September 30, 2019 was $4,556,509 as compared to $40,944 for the three months ended September 30, 2018. This increase is the result of a larger amount drawn on our credit facility in 2019, most of which was incurred in the acquisition of our Northwest Shelf assets.
Realized loss from Derivative Instruments. Realized loss on derivatives for the three months ended September 30, 2018 was $2,722,774. There was no realized gain or loss on derivatives during the three months ended September 30, 2019.
Unrealized loss from Derivative Instruments and Hedging Activities. The Company records all derivative instruments, other than those that meet the normal purchases and sales exception, on the balance sheet as either an asset or liability measured at fair value. Changes in fair value are recognized currently in earnings unless specific hedge accounting criteria are met. During the three months ended September 30, 2019, the change in fair value resulted in the recognition of a gain of $1,877,368 on derivative contracts as compared to a loss of $566,649 during the same period in 2018.
Net income. For the three months ended September 30, 2019, the Company had net income of $9,888,356, as compared to $5,693,628 for the three months ended September 30, 2018. The increase in net income primarily resulted from increased revenues as a result of the Acquisition.
Results of Operations – For the Nine Months Ended September 30, 2019 and 2018
Oil and natural gas sales. For the nine months ended September 30, 2019, oil and natural gas sales revenue increased $50,968,192 to $143,471,645, compared to $92,503,453 for the same period during 2018, primarily as a result of the Acquisition.
Oil sales increased $51,437,289 and natural gas sales decreased $469,097. For the nine months ended September 30, 2019, oil sales volume increased 1,108,412 barrels to 2,612,742 barrels, compared to 1,504,330 barrels for the same period in 2018. The average realized per barrel of oil price decreased 9% from $59.65 for the nine months ended September 30, 2018, to $54.03 for the nine months ended September 30, 2019. For the nine months ended September 30, 2019, gas sales volume increased 888,086 thousand cubic feet (MCF) to 1,697,373 MCF, compared to 809,287 MCF for the same period in 2018. The average realized natural gas price per MCF decreased 60% from $3.42 for the nine months ended September 30, 2018, to $1.35 for the nine months ended September 30, 2019.
Oil and gas production costs. Our lease operating expenses (LOE) increased from $19,638,163 or $11.98 per barrel of oil equivalent (BOE) for the nine months ended September 30, 2018, to $36,455,925 or $12.59 per BOE for the nine months ended September 30, 2019. The increase in total LOE is largely a result of an adjustment to include the processing fees associated with part of our gas production as an LOE rather than a reduction of revenue. Additionally, increase production between the periods and the Acquisition contributed as well. The increase in the per BOE rate is primarily a result of the referenced adjustment to the accounting treatment of the processing fees.
Production taxes. Production taxes as a percentage of oil and natural gas sales were 5% during the nine months ended September 30, 2018 and remained steady at 5% for the nine months ended September 30, 2019. These rates are expected to stay relatively steady unless we make acquisitions in other states with differing production tax rates or the states of Texas or New Mexico change their production tax rates.
Depreciation, depletion, amortization and accretion. Our depreciation, depletion, amortization and accretion expense increased by $13,083,437 to $41,659,494 for the nine months ended September 30, 2019, compared to $28,576,057 during the same period in 2018. The increase was primarily a result of higher production volumes as a result of the Acquisition.
General and administrative expenses. General and administrative expense increased $5,844,745 to $15,287,072 for the nine months ended September 30, 2019, as compared to $9,442,327 for the nine months ended September 30, 2018. Acquisition related costs of approximately $4.1 million was the primary reason for the increase.
Interest expense. Interest expense for the nine months ended September 30, 2019 was $9,589,434 as compared to $85,427 for the nine months ended September 30, 2018. This increase is the result of a larger amount drawn on our credit facility in 2019, most of which was incurred in the acquisition of our Northwest Shelf assets.
Realized loss from Derivative Instruments. Realized loss on derivatives for the nine months ended September 30, 2018 was $6,600,226. There was no realized gain or loss on derivatives during the nine months ended September 30, 2019.