Main Pass Area Research Articles

Abstract: Characterization and 3D Modeling of Turbidite Reservoir: A Case Study in Miocene Slope Deposits, Main Pass Area, Offshore Gulf Coast of Mexico 

ABSTRACT A case study of a detailed characterization and 3-D modeling of a turbidite reservoir has been completed. Well correlation and seismic attribute analysis revealed a clear three dimensional facies architecture of a turbidite deposit reservoir. The study shows that a turbidite lobe is developed along with multiple and relatively high density gravity flow events. Reservoir property and heterogeneity are controlled by facies architecture in a predictable pattern. The turbidite lobe has a typical mounded shape with a fairly straight feeder channel. The main body of the lobe is composed of stacked lenticular sand bodies, each representing a single gravity flow event. Reservoir sand is cleaner and thicker at the center lobe, rapidly becoming finer grained, with increasing shale interbeds, and finally pinches out towards the edge. Inside the lenticular sandbodies, thin shale patches can serve as vertical barriers to fluid flow during production. Facies distributions together with the structural pattern control the hydrocarbon resource potential and production performance in this area. They also provide important information for further exploration and development. A 3-D reservoir model is built using stochastic object based techniques. To preserve the observed facies architecture in the model, the General Marked Point Process algorithm is employed. Specific object shapes are designed in the computer program for different facies. Multiple stage facies modeling enables the preservation of different levels of reservoir heterogeneity. Major geological features are preserved in the model and can be incorporated in future flow simulations.

Abstract: Biostratigraphy and Paleoecology in High Energy, Bathyal Sedimentary Settings: Studies in the Main Pass area, Louisiana offshore, Gulf of Mexico

ABSTRACT The Main Pass area is an intersection of depositional environments, each of which leaves its own paleontologic imprint in the sedimentary record while mixing with and frequently obscuring others. High energy scouring, reworking, slumping and multiple sedimentary sources often obscure the succession of events that characterize the depositional and biostratigraphic history of the area. Paleontologic methods, such as water mass tracking and multivariate analysis of faunal succession, separate the biostratigraphic imprints of provenance and depositional energy as well as a history of water column changes that alter the depth associations of foraminiferal species. The separation of these factors allows for a minutely detailed understanding of sedimentary regimes and their dominance or recession over time, helping to characterize the types and qualities of potential reservoirs. Beneath regional unconformities in Main Pass representing the major datums are foraminiferal abundance peaks. The foraminiferal faunas of these events are, in part, characterized by cold-water benthics, usually assumed to be of deeper water affinities than those of the surrounding stratigraphic section. Another faunal characteristic of these events is the occurrence of cooler surface water planktonic species often associated with upwellings. The shoaling of deep currents prior or concorrent with lowstand is considered to be the cause for both of these characteristics. Extensive, longer term faunal changes are associated with probable changes in the source of deep and intermediate currents in the Gulf of Mexico. The interpretation of depositional energy regimes as determined by faunal response is tied directly to sedimentary setting, and yields more detailed information than estimates of paleobathymetry do. That the distribution of extant foraminifera was determined primarily by environmental energy was recognized by Uphaw and Stehli (1962) and Leutze (1972). Core data and interpretation of Main Pass seismic and electric logs were used to corroborate the environmental interpretations of the faunal abundances as described below. Figure 1 contains eight foraminifera abundance curves. These are derived from foraminiferal paleontologic data from an eastern Main Pass well spanning the early Pliocene and late Miocene. Curves 1 and 2 are total foraminiferal diversity; these predetermined statistics are provided for reference. Curve 8 is planktonic species abundance. Curves 2 through 7 are abundances for total foraminiferal faunal components separated by Q-mode factor analysis. They are arranged vertically from lowest amount of variance explained (3) to the greatest (7). The position of regional unconformities are indicated by arrows (^) at the base of curve 7. Curve 3 is dominated by species redeposited from the Florida platform. They are common in slumps and slides along the platform edge and in levee sediments along channels traced back to the platform. The contribution of this component to the sedimentary record is local and relatively constant, becoming obvious only when not overshadowed by riverine deposition. Curves 4 and 5 are regarded as representing redeposited species from riverine dominated and high energy neritic sediment sources, respectively. Curve 4 usually corresponds to the abundance of species carried by scouring sands of Mississippi River origin. The species of curve 5 are present in the scour surfaces of major unconformities and at the base of channels. The species represented by curves 6 and 7 are usually regarded as in situ, consisting respectively of moderately energy tolerant neritic species and energy intolerant species usually associated with bathyal water depths and conditions. These faunal components alternately represent, in relative abundance, the lowest energy sedimentation (condensed sections) or the highly productive periods prior to apparent lowstands. These are only a part of the depositional and paleoenvironmental features that can be segregated from high-energy sediments. Information on depositional pathways, freshwater incursion and other surface water environmental changes related to eustacy can be obtained by extension of the same statistical techniques.

Stratigraphic Framework of a Late Pleistocene Shelf-Edge Delta, Northeast Gulf of Mexico

Lithologic, biostratigraphic, and chronostratigraphic data from a 92-m continuous surface boring, in the Main Pass area of the outer Mississippi-Alabama shelf, were used to calibrate high-resolution seismic profiles in a study of a late Pleistocene shelf-edge delta. The boring is the first of its kind through a shelf-edge clinoform wedge and the first ground-truth confirmation that the clinoforms in the study area are deltaic in origin. Chronologic control for the late Pleistocene outer shelf stratigraphy is based on the identification of Ericson Zones X, Y, and Z (alternating warm and cold water planktonic foraminifera zones) in the boring, representing at least the last 130 k.y. During sea level lowering related to the previous glacial maximum, the delta system progra ed onto a carbonate-rich outer shelf and upper slope starved of terrigenous sediments. The resulting seaward-thickening deltaic wedge is more than 100 m thick in localized areas. Stacking patterns of delta lobes demonstrate overall progradation from the northeast to the southwest. The ancestral Mobile River, possibly joined by the Pascagoula River, was the fluvial feeder of the shelf-edge delta. The upper portion of the delta wedge is extensively eroded, primarily by a broad swath of significant fluvial scour centered along the northeast- to southwest-oriented dip axis of the delta, and to a lesser extent by subsequent transgressive truncation. Fluvial scour resulted in a broad erosional trough. Evidence from the boring indicates that the erosional trough is filled with fluvial and estua ine facies. Thin estuarine and overlying marine units reflect transgression of the Lagniappe delta during the late Pleistocene--early Holocene transgression. According to standard sequence stratigraphic definitions and nomenclature, the extent of the sequence boundary, identified as the erosional base of the fluvial facies, places the majority of the outer shelf delta in the systems tract. Although the sequence stratigraphic approach is strictly a methodology, the term highstand is misleading for this systems tract. The portion of the delta thus categorized was built during the falling to lowstand minimum part of the relative sea level curve. Deposits of the actual in sea level that preceded progradation to the shelf edge occur instead on the inner and middle shelf s thin (<10 m) erosional remnants. Although eustatic sea level fall was large and rapid (at least 60 m in 20 ka), fluvial incision of the shelf break did not occur. Incision is instead best developed on the inner to middle shelf (about 20 m of erosional relief). No canyon or channel features occur on the upper slope that can be associated with this shelf-edge delta.

Upper Pleistocene-to-Holocene Depositional Sequences in the North-Central Gulf of Mexico

Upper Quaternary depositional sequences and their systems tracts can be delineated in the Main Pass area using minisparker seismic data. Core collected by the Gulf of Mexico Outer Shelf/Slope Research Consortium (Amoco, ARCO, BP, Chevron, Elf-Aquitaine, Exxon, Marathon, Mobil, and Texaco) sampled these systems tracts on one site in Main Pass 303. At the shelfbreak, a distinct change in depositional style occurs across the latest Wisconsinan sequence boundary. Widespread progradational systems (late highstand systems tract) below become focused into discrete depocenters with predominantly aggradational deposits (lowstand systems tract) above. Focusing was probably a result of localized high subsidence rates due to salt movement, progradation into rapidly deepening water, and, possibly, stabilization of sediment transport paths on the exposed shelf. No age-equivalent submarine canyons are present in this area. The oldest mappable systems tract is a highstand systems tract deposited during stage 3 interstadial and the early-to-middle stage 2 glacial. The overlying transgressive systems tract was deposited coeval with the stage 2-stage 1 transition. It thins in a land-ward direction, except where an updip depocenter was present. At the corehole site, the transgressive systems tract consists of fining-upward deposits ranging from medium-grained sands to clays. The transgressive systems tract includes smallmore » slope-front-fill lenses deposited on the uppermost slope above and adjacent to lowstand deltaic depocenters. These lenses likely comprise silt and clay derived from either reworking of lowstand deltas or sediment bypassing the outer shelf.« less

Foraminiferal Biostratigraphy, Paleoenvironmental History, and Rates of Sedimentation Within Subsurface Miocene of Southern Alabama and Adjoining State and Federal Waters Areas: ABSTRACT

Miocene sedimentary rocks of the study area consist of a predominantly regressive sequence of clay and quartzose sand deposited on a carbonate platform which dips toward the southwest at 50-100 ft/mi. This clastic wedge ranges in thickness from 1000 ft in central Mobile and Baldwin Counties to a maximum of about 5800 ft in the northeastern portion of the Main Pass area. Analysis of planktonic and benthic foraminifera has resulted in a refined biostratigraphic zonation of these rocks, which indicates that basal Miocene transgressive shale assignable to the Amphistegina B interval zone immediately overlies the upper Oligocene regional carbonate platform. Thus, both lower and lower middle Miocene sedimentary rocks are absent throughout the area of investigation. Biostratigraphic analysis of the middle and upper Miocene rocks has resulted in a series of cross sections illustrating the dramatic thickening southwestward into the federal offshore continental shelf and showing the relationships of producing intervals in the Cibicides carstensi and Discorbis ''12'' interval zones. Paleoenvironmental interpretations are illustrated on a series of maps constructed for selected regional biostratigraphic zones. These maps have outlined previously unrecognized late middle and early late Miocene deltaic sedimentation in the southeastern Mobile County and Chandeleur-Viosca Knoll (north) areas. Studymore » of sedimentation rates, which range from less than 25 up to 1370 ft/m.y., further aids in understanding the deltaic and coastal shelf sedimentation of the Miocene within Alabama and adjoining state and federal waters areas.« less

Regional Biostratigraphy and Paleoenvironmental History of Miocene of Onshore and Offshore Alabama: ABSTRACT

ABSTRACT Subsurface Miocene sediments of coastal Alabama and the adjoining state and federal waters area consist of a clastic wedge varying in thickness from about 500 feet in south-central Baldwin County in southern Alabama to a maximum of about 6,000 feet in the northeastern portion of the Main Pass Area. Relatively deep-water and open-marine transgressive basal Miocene clays and shales unconformably overlie a gently southwestward dipping late Oligocene-earliest Miocene carbonate platform. Middle and late Miocene sediments consist of a regressive offlapping sequence of sand and shale deposited in varying neritic paleoenvironments. Analysis of planktonic and benthonic foraminifera has resulted in a refined biostratigraphic zonation of these sediments, permitting the recognition of several regional time-equivalent datum levels, or biohorizons. These biohorizons are shown on a series of subsurface cross-sections which indicate the dramatic southwestward thickening of middle and late Miocene sediments within the Cibicides carstensi and Discorbis 12 interval-zones. The paleoenvironmental history of the Miocene has been reconstructed on a series of paleobathymetric maps drawn for selected regional biohorizons. Among other features, these maps have proven the existence and outlined the margins of previously unrecognized shallow-neritic deltaic sediments in southeastern Mobile County and in the Chandeleur and Viosca Knoll (north) Areas. Analysis of sedimentation rates, which range from less than 25 to 1,370 feet per million years, further aids in understanding the coastal shelf, deltaic, and open-marine depositional history of the Miocene of Alabama and the adjoining state and federal waters areas.

Matrix Acidizing Design and Quality- Control Techniques Prove Successful in Main Pass Area Sandstone (includes associated papers 17274 and 17466 )

Summary. Successful acidizing techniques have been developed andimplemented in the Main Pass area, offshore Louisiana. Since mid-1984,37 oil wells have been acidized. resulting in a success rate of 95% anda total increase in production of almost 12,700 BOPD [2019 m3/d oil]. One of the primary reasons these treatments were so successful wasthe continuous injection of a finely ground oil-soluble resin divertingagent throughout all acid stages, which decreased acid injection into themore permeable zones and helped distribute the treating fluids moreuniformly. Other factors that may not be the industry norm that influenced theeffectiveness of these treatments included (1) reduced-strength HCl/HF andpreflush acids, (2) xylene solvents pumped ahead of injected acid for preflush acids, (2) xylene solvents pumped ahead of injected acid for possible paraffin and/or asphaltene removal, (3) xylene pumped after the possible paraffin and/or asphaltene removal, (3) xylene pumped after the overflush stage as a diverter breaker, (4) filtration of all fluids, (5)low-rate, high-pressure pump for continuous injection of diverterdownstream of filters, (6) use of "pickled" coiled tubing, (7) coil/production tubing annulus pressure recorder, (8) testing production tubing production tubing annulus pressure recorder, (8) testing production tubing before pumping, (9) use of boats exclusively, rather than offloaded skids, from which to mix and pump, (10) on-site acid mixing with titration checksof concentration before pumping, and (11) postjob laboratory analysis ofconcentrations and solids content of selected spot samples. Introduction The Main Pass wells acidized are located offshoreLouisiana in Blocks 288, 296, and 311, about 30 miles [48km] east of the mouth of the Mississippi River. Thirteendifferent sands, which range in depth from 4,500 to 6,500ft [1372 to 1981 m], have been acidized to date. Thenative permeabilities of these formations range from 100to 1,000 md. Other average reservoir parameters include27% porosity, 25% water saturation, and 140 degrees F [60degrees C] formation temperatures. Perforated intervalsrange from 12 to 110 ft [4 to 34 m], and the majority ofthe wells are dually completed. Of the wells acidized in this program, when completed,51 % were perforated overbalanced with 16 shots/ft [52shots/m] followed by perforation washing. The other 49%were perforated with 12 shots/ft [39 shots/m] with variousdegrees of underbalance. All completions weregravel-packed for sand control, and all completion fluid wasfiltered. Both types of completions produced some wellswith high degrees of skin damage. The formations acidized contain low quartz, high clayminerals, high feldspar, iron minerals, andlow-API-gravity crudes (15 to 28 degrees API [0.97 to 0.89 g/cm3]), which are undesirable characteristics in sandstone acidcandidates. This rock composition, combined withsand-control installations and completion fluid, is oftensusceptible to impairment, which can be chemical (such as claydamage) or mechanical (such as particulate pluggingcaused by entrained solids in the completion fluid) innature. Skin damage is a major reason many Main Pass wellsdo not reach their production potential. Determiningwhether the major cause of damage is drilling, perforating, gravel packing, or migrating fines is very difficult, perforating, gravel packing, or migrating fines is very difficult, however, each of these probably contributes to someextent. This acidizing technique was designed to increaseor to restore permeability into the wellbore with aminimum disturbance of the stabilized wellbore inflowframework by reducing skin. Few solid correlations were found between success(i.e., skin reduction) and any one of the new techniquesperformed because so many techniques were changed at performed because so many techniques were changed at once that no single item could be independently tested. Because we think that each new technique has theoreticaland practical merits, we were reluctant to reduce theeffectiveness of the job by omitting one or more for the sakeof science. Our data base is relatively small and confined to arelatively narrow, type of formation, but the techniquespresented are sound. and most are applicable to all presented are sound. and most are applicable to all sandstone acidizing. Background Since the installation of our first Main Pass platform in1970. acid stimulation has been used to restore andmaintain production rates from wells in decline. Threedistinct acidizing periods that contributed to the evolution of ourcurrent design were experienced: pre- 1978, 1978–81, and1982–84. These periods are evidence of advancingtechnology in the industry. as well as changing management philosophy. JPT P. 931

Comparison of Tertiary Depositional Sequences, Age of Bounding Unconformities, and Coastal Onlap Patterns in Baltimore Canyon Trough, Offshore New Jersey, and Main Pass, Offshore Alabama: ABSTRACT

Interpretation of high-quality seismic reflection profiles tied to well bores has delineated the Tertiary geologic history of the Baltimore Canyon Trough and the Main Pass area. During the Tertiary both areas subsided slowly, were in comparable paleographic position, and were the focus of primarily siliciclastic, progradational sedimentation. Because these areas are so similar geologically and have extensive seismic, log, and paleontologic data, they provide a unique opportunity to compare the character, timing, and extent of depositional sequences found on two different portions of the North American continental margin. The Cretaceous-Tertiary boundary is characterized by an erosional unconformity which is downlapped by overlying Paleocene clinoforms. This downlap surface is interpreted to be a result of the rapid rise in sea level in the late Maastrichtian and early Paleocene. Both areas remained in deep water throughout the Paleocene and Eocene and record second-order (5-10 m.y.) eustatic cycles. Following a major basinward shift of coastal onlap in the Oligocene, thick progradational deltaic wedges are found within the study areas which record the effects of third-order (approx. 1 m.y.) eustatic cycles. These depositional sequences may be grouped into second-order eustatic cycles recognized by major downward shifts in coastal onlap in the Oligocene, lower Miocene,more » and at the end of the middle Miocene. Landward and basinward shifts in coastal onlap patterns show a high degree of similarity among the study areas and with the global coastal onlap chart. A departure in the middle Miocene is attributed to differing subsidence histories of the two margins.« less

Correlation of Cenozoic Sediments on Gulf of Mexico Outer Continental Shelf: Galveston Area Offshore Texas to Vermilion Area Offshore Louisiana (Part 1): ABSTRACT

Detailed stratigraphic correlations of the Texas and Louisiana outer continental shelf (OCS) of the Gulf of Mexico have been conducted for the past several years as part of the geological and geophysical effort included in the resource evaluation program. Part 1 of this study includes the area from Galveston, offshore Texas, to Vermilion, offshore Louisiana. Part 2 will extend down the Texas coast to Port Isabel. Part 3 will extend eastward beyond the Main Pass area. Other parts in the series are contemplated for the eastern gulf and the deep-water areas. The study area for part 1, Galveston through Vermilion, was selected because it is centrally located and includes portions of most of the productive trends on the federal OCS, and it includes a stratigraphically complex region characterized by the transition from the deltaic sedimentary sequences of the central Gulf of Mexico OCS to the offshore bar facies of the western Gulf of Mexico. The primary objective of this investigation is to establish a regional stratigraphic correlation grid including all major productive intervals based on electric-log, seismic, and paleontological data. Twenty-five stratigraphic horizons have been identified and regionally correlated. The correlations of regional markers are presented on both electric-log (geologic) cross sections and on seismic sections that closely parallel the geologic cross sections. The regional markers correlated on the E-logs were projected onto nearby seismic sections and correlated from well to well to verify the accuracy of the electric-log correlations. Time-depth values were calculated from borehole velocity surveys and integrated sonic logs. Approximately 30 electric log and 40 seismic sections have been constructed. Work on part 1 included the detailed analyses of more than 1,500 wells, three-quarters of which had paleontological data, and the interpretation of 12,000 line-mi of seismic data. End_of_Article - Last_Page 1429------------

Perforating Resin-Consolidated Zones for Capacity Improvement

Sand control using epoxy resin consolidation usually is effective, but treated wells fail to produce occasionally. This, paper presents field results showing that through-tubing jet reperforation of wells into the previously resin-consolidated zone can restore production. previously resin-consolidated zone can restore production. Laboratory tests indicated clean, productive perforations and undamaged resin consolidation. Introduction Reservoirs from surface to 8,000 ft and deeper off the Louisiana coast are notorious sand producers. Excessive sand production can result in separation and disposal problems, erode pipe and equipment, damage casing, problems, erode pipe and equipment, damage casing, and shutdown pumps. Sand control is necessary in wells of this type. From 1958 to 1972, when multiple completions were most common, Chevron Oil Co. elected to complete many wells dually with two-stage gravel packs in lower zones and resin consolidation in upper zones. Any selective (single) zones also were resin consolidated. Both sand control methods have proven highly successful. However, in several instances some resin-consolidated zones failed to produce, and acidizing also failed to induce flow. Assuming sand or mud fillup is not blocking the perforations, it has been proposed that unintended dirt or debris injected with the resin and associated fluids may plug perforations or damage near-well formation plug perforations or damage near-well formation permeability. permeability.After all other methods failed to induce flow from these wells, reperforation with through-tubing, jet-perforating guns gave promising results. Field Work Six nonproducing or low-production resin-consolidated wells were reperforated. Two other selected wells were not reperforated because of mechanical problems encountered. The selected wells are located east of the Mississippi River delta in the Main Pass area. The productive section is Upper Miocene in age, with sands and productive section is Upper Miocene in age, with sands and shales deposited in a near-shore marine environment. As the electric logs (Fig. 1) suggest, some sands are massive and relatively clean with porosities of 30 to 35 percent, while others are argillaceous with lower porosity. The eight wells represented two different types of completion. One was the selective zone completion (Fig. 2). Casing was perforated, sand was resin consolidated and packers were placed on single tubing string, isolating the zones at initial completion. Only one zone was produced at a time, starting at the bottom and progressing up produced at a time, starting at the bottom and progressing up the tubing. When moving to an upper selective zone, lower zones were plugged off and a special tubing perforator was used to open the tubing between the packers perforator was used to open the tubing between the packers isolating the selective zone to permit flow. In contrast, when using the reperforation completion technique, the reperforating gun in a selective zone must perforate both tubing and casing. A through-tubing, expendable, capsule-type, jet perforating gun was used. Shot density was four shots per foot, oriented at a 90 degrees angle. Wells 1 and 2 were selective zone completions. The second type was the standard dual completion (Fig. 3). Two strings of tubing allowed simultaneous but separate production from both zones. In our examples, only the upper zone was resin consolidated. To reperforate these zones, the perforating gun was lowered through the short tubing string until it hung free in the upper zone. Only the casing was penetrated. JPT P. 283

Developments in Louisiana Gulf Coast in 1968

The Louisiana Gulf Coast includes the 38 southern parishes of Louisiana and 16 continental shelf areas offshore. Oil and gas are produced from strata ranging in age from Cretaceous to Pleistocene. There were 2,505 exploratory and development wells drilled in 1968, an increase of 394 from the previous year. Of the 801 exploratory wells, 21% were successful. Discovery of 26 new fields (17 onshore and 9 offshore) was made in 1968. The most important are West Manchester, Calcasieu Parish; Block 14, East Cameron Area; Block 61, South Pass Area; and Block 290 and Block 305, Main Pass Area. The most significant of the 139 new pools and extensions were at Bayou Bouillon, St. Martin Parish; Bayou Carlin, St. Mary Parish; Tigre Lagoon, Vermilion Parish; Block 204 and Block 239 Ship Shoal Area; and Block 56, West Cameron Area. Geophysical activity decreased from the previous year, mainly onshore. In 1968, 6 state lease sales and 1 federal offshore drainage sale were held. A record bid of $27,401 per acre was made on a West Delta offshore tract.

Developments in Louisiana Gulf Coast in 1967

The Louisiana Gulf Coast includes the 38 southern parishes of Louisiana and 16 continental-shelf areas offshore. Oil and gas are produced from strata ranging in age from Cretaceous to Pleistocene. There were 2,111 development and exploratory wells drilled in 1967, 18% fewer than in 1966. Of the 775 exploratory wells, 22% were successful. Of the 17 new-field discoveries (7 onshore and 10 offshore), the most important are: South Judice field, Lafayette Parish; Manchac Point field, West Baton Rouge Parish; Block 207 field, Ship Shoal Area; and Block 144 field, Main Pass Area. The most significant of the new pools and extensions are in Clear Creek field, Allen Parish; West Lake Arthur field, Jefferson Davis Parish; Block 43 field, Grand Isle Area; Block 30 field, West Delta Area; and Block 133 field, West Delta Area. Geophysical activity declined significantly from the previous year. The federal offshore lease sale in June, in which 744,000 acres were sold for $510,079,177, was the largest ever in the Louisiana offshore.

Developments in Louisiana Gulf Coast in 1966

The Louisiana Gulf Coast includes the 38 southern parishes of Louisiana and the 16 continental-shelf areas offshore. Oil and gas are produced from sediments ranging in age from Cretaceous to Pleistocene. There were 2,570 development and exploratory wells drilled in 1966, 12% fewer than in 1965. Of the 875 exploratory wells, 23% were successful. Of the 44 new-field discoveries (21 onshore and 23 offshore), the most important are: Block 133 field, West Delta Area; Coon Point field, Ship Shoal Area; and St. Amelia field, St. James Parish. The most significant of the 185 new pools and extensions include Block 6 field, Main Pass Area; Block 16 field, Grand Isle Area; Block 58 field, West Delta Area; Fordoche field, Pointe Coupee Parish; Bayou Hebert field, Vermilion Parish; and Garden City field, St. Mary Parish. Geophysical and drilling activity declined slightly from the previous year. Lease activity for the total area compared favorably with 1965.

Developments in Louisiana Gulf Coast in 1962

The Louisiana Gulf Coast consists of the 38 southern parishes and the 16 continental shelf areas off-shore. Oil and gas production is obtained from sediments ranging in age from Cretaceous to Pleistocene. The 2,236 development and exploratory wells drilled in 1962 are 2.3% more than were drilled in 1961. Of the 600 exploratory wells, 17.0% were successful. For the first time in several years the Southwest District was the most active in exploratory drilling. Of the 43 new-field discoveries (27 onshore, 16 offshore) the most important are: Money Island, Cameron Parish; Mud Point, Vermillion Parish; Block 112 field, Main Pass Area; Block 225 field, Block 229 field, West Cameron Area; and Block 41 field, West Delta Area. The most important of the 240 new pools and extensions include Couquille Bay field, Plaquemines Parish; Eloi Bay field, St. Bernard Parish; and Lake Barre field, Terrebonne Parish. Geophysical activity showed a slight increase for the first time in several years. Leasing continued to be very active but scattered. In general, 1962 compared favorably with 1961 and preceding years.