OIL POSSIBILITIES OF 1023

Oil Possibilities of Colombia

By CHESTER W. WASHBURNE AND K. D. WHITE, NEW YORK, N. Y. Downloaded from http://onepetro.org/TRANS/article-pdf/68/01/1023/2177058/spe-923023-g.pdf by guest on 27 September 2021 (New York Meeting, February, 1922)

COLOMBIA has an almost ideal situation with respect to the world's markets, being only a short distance from the Panama Canal and the West Indies. The sailing distance from its Caribbean ports to New York is less than that from Tampico. Geographically, Colombia consists of three systems of broad mountain ranges separated by two long narrow valleys. The Cauca River valley separates the Western or Coastal range from the Central range. On the west side of the Coastal range are the Atrato and San Juan Rivers. The Central and Eastern ranges are separated by the valley. In the department of Santander the Eastern range divides, one branch continuing northward as the Cordillera of Perij a, the other turning eastward across Venezuela as the Cordillera of Merida. Between these ranges is the great basin occupied by Lake Maracaibo. These valleys consist mainly of long narrow reentrants or tongues of Tertiary sediments between the older rocks of the mountain ranges. The late Miocene and younger sediments seem to have been deposited in separated basins, but the Cretaceous and possibly some earlier Tertiary strata were laid down more or less continuously over a great part of Colombia and Venezuela. These strata were subsequently folded into the present ranges. The deposition of the Cretaceous and of some of the Tertiary was in a .great sea, the main land mass being in Brazil, with land probably along some of the cores of the present mountain systems. The sediments, except the Lower Cretaceous, vary markedly in character and thickness. An illustration is seen in the massive series of non-marine conglomerates and sandstones of the upper Magdalena River valley, near Honda, which are almost wholly wanting in the coastal sections where marine sediments prevail. The oldest rocks bearing on the search for oil are the black carbonace­ ous and bituminous shales, limestones, and cherts of the upper part of the Lower Cretaceous. These probably are the main source of oil in both Colombia and Venezuela. They include thick bodies of true "oil shale." Above the carbonaceous and bituminous beds, lies a series of many thousand feet of clastic sediments. The most noticeable and easily recognizable formation among these clastic sediments is the "coal­ bearing series," which may be either upper Cretaceous or Eocene. The 1024 OIL POSSIBIL11'IES OF COLOMBIA

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horizons that have been proved to be petroleum producers in Colombia occur in this series and in the next overlying formation. The several stratigraphic sections available for Colombia are platted in Fig. 2, with tentative correlation lines drawn between formations which are thought to be nearly contemporaneous. Special thanks are due A. Faison Dixon for his aid in the correlations. For comparison, Colombia may be roughly subdivided into the following areas or districts: 1. The Santa Marta area and the Goajira peninsula. Downloaded from http://onepetro.org/TRANS/article-pdf/68/01/1023/2177058/spe-923023-g.pdf by guest on 27 September 2021 2. The Sinu River valley. 3. The Cartegena-BarranquilIa coastal region. 4. The lower Magdalena River valley. 5. The upper Magdalena River valley. 6. The Amazon River drainage, including the Meta River basin. 7. The Colombian-Venezuelan boundary region. S. The Pacific coastal plain. 9. The Atrato River valley.

SINU RIVER VALLEY The sediments of this valley are of Miocene and Pliocene age, in large part marine. They have been sharply folded and in some localities have been faulted. Sharp antielines with limbs dipping 45° or more near the crest are the rule. Elfred Beck1 describes several structures which he located east and north of the Sinu River, the most important being the Sincelejo anticline, which he traced for more than 50 mi. (SO km.) a little east of north. The eastern flank of the anticline dips from 5° to 30° while the western limb dips at 45°. In Beck's cross-section the folding becomes sharper westward and considerable faulting is shown. West of the Sinu River, between Monteria and the sea, three anticlines have been recognized and each traced about.1O mi. (16 km.). The two more eastern folds are separated by a syncline about 10 mi. wide between anticlinal axes. The anticlines are closely folded, the limbs towards the synclines having an average dip of about 45° for a mile from their crests. The other limbs are nearly vertical. The petroleum evidences on both anticlines are similar; large mud volcanoes and seepages of dark green oils come from their steeply dipping crests. The anticlines, the crests of which are in Miocene rocks, expose 7000 or SOOO ft. (2134 to 243S m.) of strata. The third anticline is situated on the sea coast, probably in Pliocene rocks. It also shows oil seepages. The petroleum evidence of this district consists of seepages of heavy

I Elfred Beck: Geology and Oil Resources of Colombia. Economic Geology (Nov., 1919). VOL. LXVIII.-65 1026 OIL POSSIBILITIES OF COLOMBIA

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tarry oils, dark green oils, gas springs, and mud volcanoes. The authors believe that mud volcanoes have little significance. Practically all oil and gas seepages are located either in the fractured core of closely folded anticlines or along fault planes. Four wells have been drilled in the Sinu River valley and another is now being drilled by the South American Gulf Oil Co., at San Andres. The first well was drilled by a Dutch company in 1910 to 1912, near San Sebastian, east of the Sinu River. It reached a depth of about 400 ft. Downloaded from http://onepetro.org/TRANS/article-pdf/68/01/1023/2177058/spe-923023-g.pdf by guest on 27 September 2021 (122 m.) and encountered a dark green oil of about 36 0 Be. gravity. It was reported to have been a 50-bbI. well. In 1915 it was badly mudded and would pump only a few barrels. The Gulf Oil Company's well is said to be located on good structure. In 1915 and 1916 The Standard Oil Co. of New York, drilled three wells to depths of about 2000 ft. (610 m.) The wells were located, respectively, 4 mi. (6.4 km.) east, 8 mi. northeast, and 12 mi. northwest of Lorica. These wells are all reported to have struck small shows of oil and gas, but nothing has been definitely proved by them. All except the shallow well were drilled quite far down the flank of the structures on which they were located. The entire region contains thick deposits of Tertiary sandstone and shale which are closely folded and much faulted. Any structure in this district deserves testing where the equivalent of the" coal-bearing" series of the Magdalena River valley, or strata close above it, may be reached by the drill, where the rocks are not too badly shattered, and where the drainage area is not too limited. With the thick shale section of the later Tertiary and with the presence of numerous petroleum seepages, well-developed folds in the Miocene and Pliocene rocks are also worthy of test, but it should be recognized that no oil horizons have been proved in these strata and that drilling to upper Tertiary horizons is much more speculative than drilling to lower Tertiary and Upper Cretaceous horizons.

CARTEGENA-BARRANQUILLA COASTAL REGION This area roughly embraces the region between the coast, the Magdalena River, and the Cartegena-Calmar railroad. In this territory about as many wells have been drilled as in all the rest of Colombia. About 6 mi. (10 kIll.) southwest of Puerto Colombia, at the village of Perdices, seven wells had been drilled up to the beginning of 1918, all within 1000 ft. (305 m.) of each other. An eighth well is located some 3 mi. east of this locality. According to Alfred Beck, the drilling was commenced by a Canadian company in 1907, and was continued in 1912 or 1913 by the Kelly Oil Co. Of these eight wells, the deepest, No.6, Perdices, was drilled to 3030 ft. (923 m.). This well encountered showings of oil and gas at 1028 OIL POSSIBILITIES OF COLOMBIA various horizons, and at 2443 to 2446 ft. (745m.) in a sandstone, 3,000,000 cu. ft. (85,000 cu. m.) of gas was reported. Well No.1, Perdices, had the best showing; salt water and oil, with a gravity of 32° Be., were reported at 135 ft. (41 m.), while in a broken sand and shale formation at 745- 754 ft. (230 m.), oil of 43.4° Be., which flowed naturally and on the pump made 140 bbl. in 7 hr., was reported. In 1917 the well was badly mudded but pumped about Y2 bbl. a day. The other wells, which were drilled to

depths of 1600 ft. (488 m.) or less, encountered shows of oil and gas. Downloaded from http://onepetro.org/TRANS/article-pdf/68/01/1023/2177058/spe-923023-g.pdf by guest on 27 September 2021 The Three Seas Oil Co. is now drilling a deep test in the Per dices region at no great distance from the other wells. Beck states that the drilling has been on a steep, narrow, poorly defined fold. At Turbaco, a station on the Cartagena~Calmar railroad, the Martinez Oil Co. drilled five wells, beginning in 1908. The first four wells were drilled with a Keystone machine to a depth less than 500 ft. (152 m.). They were all located close together in the immediate vicinity of numerous and active mud volcanoes, which had been given prominence by their description by Von Humboldt. In 1912, another well was drilled about a mile south of the mud volcanoes, by the Martinez Oil Co., with a stand­ ard rig. It went to a depth of about 2200 ft. (671 m.), its log showing remarkable uniformity in rock strata. This is readily explained by an excavation 500 ft. east of the location, where strata striking N. 40° dip westward from 75° to vertical. The surface evidences of petroleum in this district are large, active mud volcanoes, gas springs, and seepages of dark green oil. Unfortu­ nately, none of the drilling seems to have been on large, well-formed structures. The drilling on suitable structures in this region seems to be amply justified.

LOWER MAGDALENA RlV~m VALLEY This is one of the two areas that have been proved to contain com­ mercial oil deposits. The field is about 300 mi. (483 km.) from the mouth of the Magdelena River, and 20 to 25 miles eastward, up the Colorado River. The discovery well was drilled in April, 1918, by the Tropical Oil Co., after abandoning the first two wells, at about 600 ft., owing to great difficulty with caving. Of the three producing wells, No.1, drilled I 2300 ft. (700 m.) was good for 3500 bbl.; No.2, drilled 700 ft. (213 m.), •i 700 bbl.; No.3, drilled 1500 ft. (457 m.), 1500 bbl. The gravity of the oil was between 42° and 45° Be. The company was purchased in 1920 by the Standard Oil Co. of New Jersey, which has built a railroad from Barranca Bermejo to the field and has shipped in large supplies of pipe, casing, tools, etc., preparatory to extensive developments. I North of the Tropical Oil Company's property, on the Lebrija River, the Colombian Syndicate has drilled several wells, all of which had (IiI showings, though none produced appreciable amounts. CHES1'ER W. WASHBURNE AND K. D. WHI'fE 1029

At Zambrano, which is about 100 miles (160 km.) from the mouth of the Magdalena River, two wells have been drilled, one by the Shell interests, the other by the Transcontinental Oil Co. The Transconti­ nental well, at between 700 and 800 ft. (213-244 m.), struck a big flow of salt water in a sand 150 ft. (45 m.) thick. The well is located on the plunging end of an anticline. The Standard Oil Co. of California is drilling two wells, about 8 mi. (12.8 km.) apart, near EI Carmen and San Jacinto, about 60 km. Downloaded from http://onepetro.org/TRANS/article-pdf/68/01/1023/2177058/spe-923023-g.pdf by guest on 27 September 2021 southeast of Cartagena, on the large concession of the Latin-American Petroleum Corpn. The San Jacinto well had a good show of oil and gas at 756 ft. (230 m.). The wells are in good structure. In this region there are large deposits of asphalt or brea, active seepages of dark green oil, gas springs, and veins of devolatilized asphaltum varying from gilsonite to grahamite. Here the large deposits of asphalt and hydrocarbon veins are restricted to the east side of the valley. In crossing the Lebrija River region eastward from the Magdalena River, the first encountered rocks dip west; on the west side of the Magdalena River the rocks dip eastward. The syncline is coincident with the Magdalena Valley as far as EI Banco, from which place it narrows and continues with more complicated structure up the valley of the Rio Cesar. Since the occurrence of oil in commercial quantity is now proved, one should test any structure that is not too contorted, under which the drill can reach the coal-bearing series or strata just above it.

UPPER MAGDALENA RIVER VALLEY This refers to the region above La Dorada, the head of navigation of the lower Magdalena. It includes the Honda district, where recently there has been considerable leasing and some drilling. The region has numerous small anticlines. Its major structure is a series of great north-south block-faults, the throw of some of these being many thousands of feet. There are two main lines of seepages. One is along the east side of the Magdalena valley, or the west foot of the second range of the Eastern , locally called the Cordillera de Sargento; the other follows the west side of the valley, or the east foot of the Central Andes. Most of the seepages below Guataqui consist of heavy asphaltic oil or brea, while most of those above Guataqui consist of dark green oil, but exceptions occur. An overlap of Tertiary strata conceals the structure in the older sedimentary rocks in many places along the east base of the Central Andes. There are exceptions to this, as at Chaparral, where there is an anticline with a large deposit of brea. The seepages of the Eastern Andes occur either on small folds or along fault planes. They are located 1030 OIL POSSIBILITIES OF COLOMBIA either Hear Lhe Lop of the Lower CretaeeollH Llaek shale.s aud lime.stolle.s or in beds a few hundred feet higher. Three wells have been drilled. In 1918 the Carib Syndicate drillecl a 700-ft. (213 m.) hole about 3 mi. (4.8 km.) southwest of the San Felipe railroad station. A little tarry oil was found in the bottom of the hole, which stopped in schist. In 1921 the Transcontinental Oil Co. drilled a well about 15 mi. (24 km.) southeast of Honda, to a depth reported at 3300 ft. (1005 m.) Downloaded from http://onepetro.org/TRANS/article-pdf/68/01/1023/2177058/spe-923023-g.pdf by guest on 27 September 2021 stopping in black limestone. From 800 to 2000 ft. (244-610 m.), several shows of oil and gas were encountered. Near Guataqui, the same com­ pany is reported to have drilled 1170 ft. (357 m.) and to have encountered small showings of oil. In the upper Magdalena River valley there are two long lines of seepages, and many small anticlines which give promise of producing oil. Whether the quantity can be sufficient to justify the cost oftransportation to the coast is doubtful. The problem of this region is one of transpor­ tation and quantity of oil, rather than the actual presence of oil, which can hardly be questioned.

ESTIMATED AREA OF POSSIBLE AND PROBABLE OIL LANDS The three wells producing in the Tropical Oil Company's concession, and the one on the Barco concession, indicate a certain amount of com­ mercially proved and highly probable oil land, but the present stage of development at these two places is not sufficient to enable us to estimate either the proved acreage or the probable production from proved land in Colombia. All we can say is that, on geological evidence, we think there is roughly 5 sq. mi. (13 sq. km.) of "probable" oil land in the two fields mentioned. On account of the small number of wells drilled, the rest of the attractive acreage must be thrown into the" possible" class. In the Magdalena Valley above El Banco, there may be 20 to 30 sq. mi. (52-78 sq. km.) of possible oil land in addition to the probable oil land above mentioned. Below El Banco it is necessary to consider the Magdalena River valley in connection with that of the Rio Sinu, with which it has close relationship in many ways. Although we have worked in several parts of this region we do not feel competent to estimate the possible oil areas within it. The anticlines generally are narrow and sharp, and on most of them it is not possible to reach the base of the Tertiary. In other words, most of them may never produce oil. The district, how­ ever, is highly attractive because of the possibility that oil may have migrated long distances upward into the attainable Tertiary strata, and because the Marine Tertiary of this region offers attractive possibilities as an additional source of oil. Our best guess is that there may be 30 sq. mi. of possible oil lands in this district. I CHESTER W. WASHBURNE AND. K. D. WHITE 1031

Concerning the Atrato River valley, neither of us knows anything. The region is very unhealthy. We understand that geologists have reported favorably on parts of this territory, but we cannot make any estimate concerning it. The west coast of Colombia, so far as we can ascertain, has no known potential oil lands. There generally is only a narrow strip of unaltered strata west of the metamorphic and igneous rocks of the mountain mass, except north of the Rio San Juan, where the old rocks disappear; and also Downloaded from http://onepetro.org/TRANS/article-pdf/68/01/1023/2177058/spe-923023-g.pdf by guest on 27 September 2021 near the south end of Colombia, where there is said to be an embayment of Tertiary in the older rocks. Our information is inadequate for much comment on the three other districts mentioned in the subdivision, namely, the Santa Marta areas and the Goajira peninsula, the Amazon River drainage (Meta River basin), and the Colombian-Venezuelan boundary area. In the Colombian-Venezuelan boundary region the Barco concession in Colombia and the Colon Development Company's property in Vene­ zuela have been partly tested. The Colon Development Co., since 1914, has drilled four productive wells on the north side of the Rio de Oro and on the Rio 'rarra. One of the Rio de Oro wells had a good flow of 27° oil at about 1000 ft. (305 m.) and another well had 32° oil of good refining quality at about 2000 ft. A shallower well, reported at about 800 ft. (244 m.), had oil of about 23° Be. The exact size of these wells is unknown but they indicate the presence of an oil field in that region. In 1920 the Colombian Petroleum Co. drilled on the south side of the Rio de Oro on the Barco concession. The well is reported 800 ft. deep and good for 500 bbl., with a gravity of about 27° Be. The company is preparing to drill on the Rio Tarra. Oil seepages are reported in places along the entire eastern front of the Cordilleras, including the Meta River basin; the geology is known to be attractive, but the transportation problems seem forbidding.