Petrography and Stratigraphy of Seville-Trident Exploration Wells Near Deming, New Mexico
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Petrographyandstratigraphy 0fSeville-Trident exploration wells near Deming,New Mexico byBusse// E. Clemons,Professor of geology, New Mexico State University, Las Cruces, NM 88003 Abstract Methods Petrographicanalyses of cuttingsfrom four wildcatoil andgas exploration Well cuttings of varied intervalswere washed and scannedunder wellsdrilled by Seville-TridentCorp. near Deming, New Mexico,from 1981 a binocularmicroscope. The selectedintervals depended on the col- to 1983are reported. Thickness of upperTertiary-Quaternary basinfill south- lectionintervals available, types of lithologiespresent in the cuttings, eastof Demingis interpretedto be about4,000 ft. Basin-fillsediments overlie in lithologies.Eighty-five about5,000 ft of Miocene-Oligocenevolcaniclastic rocks and ash-flowtuffs. and bracketingdistinctive changes petro- TheMiocene-Oligocene rocks overlie up to 3,600ft of RubioPeak Formation (Eocene),which is intrudedby a fine-crystallinequartz monzonite The No. 2 City of Demingwell was drilled to a depth of 12,385ft and bottomedin o/ RubioPeak Formation. The o^ No. 1 McSherrywell wasdrilled to a depthof -1 tttl, 12,495ft, but cuttingsare available only to 12,430ft. About300 ft of probable 2r- PaleoceneLobo Formation is interpretedbeneath the RubioPeak Formation -A andabove about 570 ft of Precambrianmetamorphic rocks. The No. I Hurt z :: Hill Ranchwell, westof Deming,is reportedto have6een drilled to a totaldepth ,. t- of 7,723ft. About 2,300ft of basinfill, 4,800ft of Tertiaryvolcanic roiks intrudedby rhyolite of Red Mountain,and M0 ft of El Paio Dolomiteare \1, representedin the cuttings(deepest cuttings studied were from 7,640ft). Silve Introduction Seville-Trident Corp., of Carlsbad, California, drilled five wildcat oil and gas exploration wells in central Luna County from 198Lto 1983(Fig. 1.).All were completedas dry holes and no shows of oil Big Eurro j MrsMfs ,.='lr f+'$.X.{r,o.*'"""",-2/S.{fii| t,,i. ,,,,,,,..,.,,,.s>)lKl)tiI e,2; x' z Ronch ittle Florido Mfs ;>,"'? oo.. Vlctorio Mts"Hurt 7,723 SrofePork S i n) ?,,,nS-Florido Mts :"i,1,9.q,'.,. '',trtttr,,"4,,.L/, "rir|. oto20 Hochito o ro ?o 30k olum bus Burro uplift. Deming Airporl T23S T24S 5 l Nol Mc Sherry Peak Formation. Third, faults are difficult to detect in the thick, Dt2,430 variedlithology,volcanic sections. Fourth, cavingsof uphole material TD 12,385 during drilling appearto havebeen common and often areabundant --D r\.0 | ily j c Sewoge-l---z-rodisposol I of Deming FIGURE l-Index maps, showing locations of five Seville-Trident wells and the surrounding irea. The blue rectangle in the top map represents the approximate location of the more detailed bottom map. Neu Mexia Geology February 7986 WEST EAST $aphic thin sectionswere prepared from No. Demingwell cuttings, 138were pre- 1 City of No. I No. 2 No.I No.I pared from No. 2 City of Deming well cut- Hurf Ronch City of Deming CilY of Dcming McSherry tings,110 were prepared from No. 1 McSherry sec. 8, T24S, RIOW sec. 6, T24S, R8W sec. 6, T24S, R8W sec. 4, T24S, RBW well cuttings, and 55 were prepared from 660 FNL, 1,980 FWL 1.650 FS a EL 6 60 FS&EL 1,980 FS A WL No. 1 Hurt Ranch well cuttings. Petro- elev. 4,4O7 tl elev. 4.282 ll elev 4,275 tl elev. 4,255 ft graphicanalyses of the thin sectionsincluded identificationof rock types and point count- mi ing 100grains on eachslide. (Photocopiesof bosin ll mi u-5 ml 1.5 fitl all grain countsare availablefrom the author upon written request.)It was not considered oosrn bosrn bosin significantto count more grains becauseof 2,200 fitl fill titl the varied interbedded lithologies and the _r\o_li!e _ 2.700 apparentabundance of cavedmaterial. Miocene- Cuttings were collectedby the operator Oligocene from the No. 1 City of Deming well at 5-ft volconics 4.O80 4.225 ,o80 intervalsbetween 800and 4,225ft. Cuttings 4,500 from the No. 2 City of Deming well were S6o level collected bv the operator at 10-ft intervals rhyolile Miocene- :T; of Oligocene between 4,-000and 72,385 ft. Cuttings from Red Mtn. ol^ Miocen e- the No. I McSherry well were borrowid from volconrcs Oligocene 313 voI conr cs Bureau Mines Min- o,ovu wilh some lo the New Mexico of and {u5-io-PioT -1 oi eral Resources and are in envelopes of 30-ft ^-fm.* 7,200 mo nz onrle l- El Poso Fm inlrusive intervals between depths of 1,200 and 12,430 7.723 ft. Lithologies of these cuttings were com- pared with the gamma-ray and neutron-den- logs to verify lithologic changes and to 8,700 sity Rubio )eok Fm. 9 9,O5O Rubio peok Fm. ,ooo further correlate the dominantly volcanic RubioPeok :t ,340 lithologies with the wire-line logs. Cuttings Fm. ond mon from the No. 1 Hurt Ranch well were col- monzonile zonile inlrusive lected at 10-ft intervals between 400 and 7,640 intrusive 10.900 ft. Reported total depth is 7,723 ft, but be- Fm. lubio Peo Lobo IJ cause of lost circulation, no cuttings are Fm monzonile ll ll available below 7,640 ft rrecombrior l2,495 Petrography FIGURE 2-Interpreted columnar sections of the four Seville Trident wells were studied. Preliminary scanning of cuttings under the binocular microscope and petrographic ex- intersertal, pilotaxitic, and hyalopilitic tex- olite of Red Mountain increases with depth amination of about 50 thin sections indicated tures are well represented and micropor- from cryptocrystalline-aphanitic at the sur- that 10 constituent litholoeies could be rec- phyritic hornblende-andesites are common. face to holocrystalline-aphanitic texture re- ognized consistently with relative ease and Cuttings also represent less abundant mafic sembling a microgranite in the deepest certainty. Constituents in fine-sized cuttings rocks containing microphenocrysts and cuttings (Fig. 7). are counted as individual grains even though granules of pyroxene, olivine, and magne- Some rhyolite and chert cuttings are dif- they may be parts of larger rock fragments. tite. Plagioclase laths in some pilotaxitic tex- ficult to differentiate. Thin sections of known For example, fine cuttings of a volcanic ar- tures are as small as 0.002mm wide and 0.025 rhyolites and cherts from mountains in and enite composed of medium (or larger) sand mm long; a few of the intergranular textures around the Mimbres Basin show that gen- grains can yield silt to fine-sand-sized frag- have equant and tabular plagioclase crystals erally the cherts are anhedral-equigranular ments of andesite, rhyolite, ash-flow tuff, up to 1 mm in size. Random estimates of and typically contain minor amounts of cal- carbonate (cement), and mudstone (matrix) plagioclase compositions based on extinc- cite. The rhyolites are less commonly equi- composition. Cuttings of ash-flow tuffs con- tion angles ranged from Ab* to Ab,, with an granular and typically contain microlites and tain individual crystal fragments of quartz, average of about Ab.. (calcic andesine). crystallites. Some small cuttings of devitri- sanidine, and plagioclase as well as tuff ma- fied shard-free matrix from ash-flow tuffs may trix. These and other possible associations be indistinguishable from rhyolites. Rhyolites need to be considered when interpreting the graphs in Figure 5. Relative percentages of Included under the heading of rhyolites Ash-flow tuffs the following 10 components were deter- are the silicic flow and intrusive rocks with mined using point counts: andesites, rhyo- hypocrystalline, anhedral-equigranular, Ash-flow-tuff cuttings were derived mostly lites, ash-flow tuffs, volcanic arenites, single spherulitic, hyaline, and seriate textures. Most from vitric and vitric-crystal ash-flow tuffs to exposed in the Little Florida, grainsof quartz sanidine/plagioclase1Fig. 3), qlrartz and feldspar crystals are less than 0.3 similar those plutonic rock fragments (Fig. 6), intrusive mm long and the average size is about 0.05 Tres Hermanas, and Grandmother Moun- rocks (excluding rhyolites and andesites), mm. Blocky oligoclase and biotite micro- tains; Cooke's, Cedar Mountain, and Black sandstone/siltstone/mudstone,carbonate rock phenocrysts are in a few cuttings; a few sub- Ranges; and Klondike and Carrizalillo Hills fragments, and chert. hedral biotite and plagioclase(?) microlites are (Clemons, 1982a,b; Elston, 1957;licha, 1954; about 0.02 mm. The basin-fill sediments in Thorman and Drewes, 1,979). Quartz, sani- No. 1 and No. 2 City of Deming and No. 1 dine, plagioclase, and biotite crystal frag- Andesites McSherry wells, to depths of 3,400 ft, contain ments (averaging <0.5 mm) are contained in All intermediate to mafic. aphanitic and grains of perlitic obsidian probably derived a cryptocrystalline and hyaline matrix. The aphanitic-porphy ri t ic rocks are'i ncl uded u n- from the Little Florida Mountains. Rhvolite majority of ash-flow-tuff cuttings contain der this heading. Most of the cuttings appear in the No. 1 Hurt Ranch well (Fig.2) is con- cuspate and platy, axiolitic shards and pum- to have come from relatively unaltered vol- sanguineous to the Red Mountain rhyolite ice shards, but ash-flow-tuff cuttings without canic and hypabyssal rocks. Intergranular, dome. The degree of crystalinity of the rhy- shards also are common. Devitrified bands February 1986 Nm Mexico Geology in these shard-free tuffs closely resemble in- grained sandstonesand conglomeraticvol- with abundant iron oxides; epidote and trusive and flow rhyolites. caniclasticrocks. They arecomposed of vary- chlorite mav be present. Thesearenites are ing proportions of basalt, andesite, latite, generally cemenied with calcite but a few dacite,rhyolite, and ash-flow-tuffrock frag- containmicrocrystalline quartz cement.Cut- Volcanic arenites mentsalong with abundantplagioclase crys- tings from these rocks appear more altered The volcanic arenites are fine- to coarse- tal fragments.The matrix is typically clay rich than cuttings from volcanic intrusives and FIGURE 3-Photomicrograph of rounded grains of quartz (Q), sanidine (S), FIGURE4-Photomicrograph of intrusive consisting of sericitized plagioclase Plagioclase(P), and varied volcanic rocks (v) from 4,040-ft depth in No.