Mustang Island Research Articles

Factors Affecting the Distribution of Opposing Mollusk Values

ABSTRACT Statistical treatment of collections of valves of the clam Dinocardium robustum deposited on the beach of Mustang Island, Texas, indicates the differences in the number of left and right valves are significant at the 0.05 level of probability. A relationship is shown to exist between average valve length and the percentage of excess valves, with the number of excess valves being significant only in collections having an average valve length greater than 69.5 mm. This relationship is attributed to a similarity in surf requirements for separating opposing valves and transporting large valves, namely a high energy surf. Differences in weight, ornamentation, and fragility between opposing valves do not affect their distribution. Boring snails attack left and right valves in equal n mbers, but seem to prefer small sizes. The size-frequency distribution of collections are varied, but highly skewed curves predominate.

Dune Cross-bedding on Mustang Island, Texas: GEOLOGICAL NOTES

The most diagnostic features of the eolian cross-bedding of Mustang Island are: 1) the large percentage (27%) of cross-beds that have dip angles greater than 30 degrees and the high mean inclination (24 degrees ); and 2) the bimodality of dip directions with modes to the N. and WSW. The bimodality is attributed to the migration of asymmetrical pyramidal dunes, a dune form that develops as an intermediate step in the transformation of barchan to longitudinal dunes as sand migrates inland. The mean standard deviation of dip azimuths of Mustang Island cross-beds (75 degrees ) is intermediate between most fluvial and marine cross-beds; it is based, however, on a bimodal distribution. The Mustang Island dunes indicate that eolian cross-bedding need not be either highly unidirectional or highly dispersed, and need not be characterized by sets of great thickness.

Completing High Pressure Gas Wells - Mechanics and Problems

Introduction This discussion is limited to high pressure gas wells or wells with abnormal pressure gradients. It does not cover extreme high pressure gas wells such as have been recently completed on the Gulf Coast where shut-in tubing pressures have been recorded in the vicinity of 12,000 psi. It is realized that such wells would probably be of more singular interest; however, since relatively few have been completed to date, the data are very meager. It is the purpose of this paper to review some of the mechanics and problems involved in the completion of high pressure gas wells. Generally speaking, completion practice refers to operations which take place from the time the well is drilled through the productive zones and continues until the well is placed on production. The wells which will be discussed might be termed as medium high pressure gas wells having pressure gradients of about 0.8 psi/ft of depth. Three gas wells in this category were recently completed in the Gulf of Mexico approximately three miles off the Texas coast near Mustang Island. The completion of these wells will be discussed in detail. Casing Program The proper design of casing programs for high pressure gas wells is of utmost importance. This is particularly true of offshore wells where the safety of personnel and equipment is at stake. For this reason the factors of safety must be maintained well within the accepted limits. The program for all three offshore wells followed the same general pattern except for the 5-in. OD oil string. Due to trouble encountered with sticking in the deviated hole, the oil string was swaged to 4.5-in. OD at the bottom of the 7-in. OD casing at approximately 10,600 ft. The typical program is shown in Table 1. Total average weight of tubular goods used in each well was 1,257,000 lb or approximately 628 tons. For the sake of simplicity the details of completion of Well No. A–3 will be discussed since all three wells were completed in the same manner.

Differentiation of Beach, Dune, and Aeolian Flat Environments by Size Analysis, Mustang Island, Texas

Mustang Island is a 16-mile-long barrier island on the south Texas Gulf coast. Sediments consist of very well sorted fine sands (mean size 2.82phi , average sigma I = 0.29phi ), and show exceedingly uniform properties lengthwise of the island. Beach, dune, and aeolian flat environments can be readily distinguished by size analysis. The best means of differentiating them is by plotting skewness versus kurtosis inasmuch as the geologic processes at work have their greatest effect on the tails of the size distribution. Beach sands form normal carves, dune sands are positively skewed but still mesokurtic, and aeolian flat sands are positively skewed and leptokurtic. Sands from the beach are more poorly sorted than those from the other two environments. These differences are extremely significant with P values between .0002 and .0000001. To explain these changes, it is proposed that as sand travels from the beach to the dunes, the coarse end of the parent normal population lags behind, rendering the size curves better sorted and also positively skewed. The aeolian flats are believed to be subject to infiltration of silt from the atmosphere; this imparts a tail of fines, registering a marked increase in kurtosis.

Differentiation of Marine and Sub-Aerial Sedimentary Environments by Volume Percentage of Heavy Minerals, Mustang Island, Texas

ABSTRACT The marine and sub-aerial sedimentary environments across Mustang Island, Texas, can be differentiated by the volume percentage of heavy minerals in the sediments. The barrier island sediments average .45% heavy minerals and the gulf sediments average .04% heavy minerals. The berm, averaging .34% heavy minerals, is the transition zone between the environments. Analyses of the amount of heavy minerals may be valuable in characterizing the environment of deposition of ancient sediments.

Log Interpretation Problem in Low Resistivity Sands

Abstract All recent investigations have attributed low electric log resistivities in producing formations to a conductive ion layer associated with clay material present in the sands. In this study another mechanism is proposed. It is believed that connate water saturation variations (which may or may not be associated with shale contact) also contribute to low resistivities. In addition to the mechanistic studies, evaluation of various recently proposed interpretation methods have been made. Of these, the Poupon, Loy, and Tixier and de Witte methods seem best. Statement of Problem Low resistivity sands are often encountered which turn out to be commercial hydrocarbon zones but appear from electric log data to be water bearing. Adequate methods of recognizing these cases are needed. Industry-wide interest in this problem is evidenced by the number of papers published in recent years. It seemed that several zones in the Mustang Island field (Nueces County, Tex.) were affected by the shaly sand problem. This was evidenced by:low hydrocarbon saturation calculations from logs and measured formation factor data in producing zones,changes in apparent measured formation factors with changes in water resistivity, andcore descriptions which indicated the presence of shaly "streaks" or "spots." A section of a typical log is shown in Fig. 1. All sands on this log are hydrocarbon zones. Scope of Investigation The Mustang Island field, Nueces County, Tex., has been chosen for the study of the shaly sand problem because the oil-water contacts are well established for most of the sands and some core data were available for study. This problem has been approached by both empirical and experimental methods. The empirical portion of this study is a comparison of calculated hydrocarbon saturations from logs by various methods with expected or known production (oil, gas, or water).

Records of Kogia breviceps from Texas, with Remarks on Movements and Distribution

Kogia breviceps (Blainville), the pygmy sperm whale, has been recorded repeatedly from the Atlantic Coast of North America (Hobbs, 1885; True, 1885; Allen, 1941, and papers cited therein; Ulmer, 1941; Enders, 1942; Brimley, 1946; Moore, 1953), but to date the only published report from the Gulf of Mexico is that of Moore (1953: 129), based on an adult that washed ashore in November, 1949, on St. Petersburg Beach, Pinellas County, Florida, and there gave birth to a calf. First specimen from Texas .—Almost a year earlier, on December 27, 1948, another adult female (PL I, Upper and Middle) was stranded near the north end of Mustang Island, Nueces County, Texas, a mile south of the Aransas Pass jetties. It was examined while fresh (with blood draining from its mouth) by staff members of the Institute of Marine Science, in the absence of the first author. Photographs were taken and the head was buried on the Institute grounds, but these circumstances were not reported, because the specimen was thought to be a blackfish. The photographs were later shown to Raymond M. Gilmore, who saw that they represented the rare pygmy sperm whale, and to Hubbs, after the second specimen had come to light in Texas. Information on the buried head enabled Gunter to disinter the skull (PL II), minus the teeth and the lower jaw. Certain differences seem to be indicated when the proportional measurements of the Mustang Island specimen (Table 1) are compared (Table 2) with those of Hubbs (1951: 507), for a California specimen, and of Enders (1942, Fig. 2) for a New Jersey specimen. Not many measurements are similar, because standardized criteria have not yet been developed, but seven measurements were the same or can be estimated with …