TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractTrinidad and Tobago is endowed with abundant oil and gas reserves both onshore and offshore. Most of the reserves offshore have been found in the shallow water shelf area. Over the last couple of years exploring the deep waters beyond the shelf (>1000 meters) has been looked at with much anticipation. However, the eight (8) wells drilled thus far have not found hydrocarbons in commercial quantities. It is important to note however, that many geo-scientists believe the exploration work in the deepwater proved the existence of a working hydrocarbon system.The drilling phase of the exploration activities in the deepwater blocks (i.e Blocks 25(a), 25(b), 26 and 27) produced many challenges. This paper will look at the major problems, risks and uncertainties encountered during the drilling of these wells and highlight key learnings that would be useful for further drilling in the deep and ultra deep waters off Trinidad and Tobago. The major well objectives will be perused to determine if these were actually attained.Results showed that some of the wells were unable to reach their technical objectives. As a result the actual number of days and cost for some wells were less than originally planned.
Several dry-hole wells drilled during the period 1999 to 2003 was the outcome of deepwater drilling to date in Trinidad and Tobago. One of the objectives though of the deepwater drilling phase was to monitor the seabed to assess the fate and effects of discharged cuttings at the drill-site locations. A monitoring plan was prepared by the operators to assess the amount, extent and effect of synthetic cuttings depositions. These effects include toxicity, water column effects and whether synthetic based muds bio-accumulate or biodegrade. Synthetic based mud is frequently used in deepwater drilling to assist in difficult drilling situations such as well bore stability, high temperatures and pressure, hydrate formation prevention and drilling time reduction. Computer model predictions were done on synthetic based mud cuttings deposition. The monitoring program includes video surveys, using sedimentary gauges and sedimentary traps. The focus of this paper will be to look at and assess the monitoring plan, discuss the results from the monitoring surveys and compare with computer model predictions. Introduction Field monitoring provides a direct means of assessing the fate and effects of drilling fluids and cuttings discharged into the marine environment. Studies have shown the energy of the water column and sea floor environment are very important in determining the extent and duration of environmental effects. Scientific data indicate that the local conditions of current, depth, temperature and the amount of materials discharged all play a critical role in determining the severity and extent of effects on seabed biological communities. Summary of our Deep Water Environment The following is a summary of the environmental conditions deepwater blocks situated in Trinidad's East Coast Marine Area. (Fig.1 shows deepwater blocks)Water Depth 1000 meters and greaterSeafloor is flat, rather featureless, mostly soft clay and silt mud.High Current area, arising from strong eddies.Seafloor seeps and mud volcanoes in the region.Fauna typical of soft bottom deepwater habitat. Ocean Current Patterns Fig 2 shows the general current patterns in the region. The deepwater area is dominated by the Guiana Current, which has a seasonal variability that is strongly dependent on both the flow from the Orinoco River and the corresponding variability in the strength of the trade winds. The Guiana current is a continuation of the South Equatorial Current. It is strengthened by outflows of the Orinoco River and other mainland rivers. The Guiana current splits at the southeast tip of Trinidad, one branch flowing northward along the east coast, and the other westward through the Columbus Channel. Marine Ecology Benthic Ecology.Macrobenthic organisms living in the bottom sediment play a major role in the marine environment since they are components of the food chain, providing especially for juvenile fish, shrimp and other macro fauna.They are effectively sessile and act as integrators of the effects of a variety of "disturbances".In this respect, they are good indicators of the quality of that environment. The benthic community structure (its species diversity and abundance) is determined by primary production in the water column, the bottom sediment type and the surrounding physio-chemical conditions. Either of these parameters or a combination, is responsible for the status of the macrobenthic community present. It is believed therefore that all marine benthos in the overall east coast of Trinidad are maintaining healthy and diverse communities.
Trinidad and Tobago has become a major player in the export of natural gas and gas related products over the past decade. This reflected a deliberate policy change within Trinidad and Tobago. It involved significant investment in people, technology and infrastructure and has enabled us to exploit several niche as well as some conventional markets that were previously inaccessible. Our markets have expanded from the Caribbean and North America to Europe, Asia, the Orient and Latin America. This paper discusses some of the steps taken towards developing a small gas based economy and ensuring its sustainability. We will briefly discuss The major gas based industries that have been developed; which include Liquefied Natural Gas (LNG), Methanol and Ammonia Production growth from insignificant to world class; in terms of natural gas as well as in the previously mentioned industries Reserves fluctuations; how they are perceived and what does it mean in terms of sustainability Growth of the economy; from a national budget of under 12 billion US dollars to over 50 billion in less than 10 years What is being done to encourage sustainability The Trinidad model is currently being considered by other states and this paper could help in their decision process.
Over the last decade, batch drilling has become increasingly prevalent in the petroleum industry as large and small investors alike seek to increase their profit margin. The perception of many of these oil companies was to drill and complete wells in batches with the hope of significant reduction in developmental cost for the field. That is, similar hole sections of different wells were drilled one after the other, the thinking being that efficiency and profits would be greatly increased. One would therefore ask the question: Could batch drilling be used to develop marginal amounts of petroleum reserves anywhere in the world? With respect to the experiences in Trinidad and Tobago, we have seen from several batch drilling projects that this type of drilling exercise may not be economical because of the geological makeup of our reservoirs. This paper looks at the experiences of two such batch-drilling projects in Trinidad and Tobago and explores the cost effectiveness of such drilling, in our very complex and uncertain geology. Introduction Batch drilling was recently done in two fields on the West Coast (Gulf of Paria) of Trinidad. These fields were prolific producers in the 1970's with one platform being among the largest in the world at the time of its commissioning. Needless to say these fields are now mature and new ways are being sought to recover remaining reserves in an economic manner. These two projects were chosen as they were drilled using the same Drilling Rig and thus economics could easily be compared. It must be noted that at least one follow-up paper can be expected to further look at Batch drilling on the East and North coasts of Trinidad. Project A Project A proposed three wells to be drilled of a cluster platform. The primary objective of these development wells was the prolific Cruse sands. Expected net oil sand was 200 ft with estimated recoverable reserves of 280 MSTB per well. For this project the top 17–1/2" hole section was to be batch drilled and cased with 13–3/8" casing. There were three main reasons for this:A previous well in this area encountered a steeply dipping, abnormally pressured water sand around 900 ft SS. Complications due to this water sand resulted in a poor cement job which led to an underground subsea breakout approximately fifteen feet from the conductor. This well bore was eventually abandoned. Hence batch drilling was proposed as a means of ensuring that this water sand was safely drilled and cased before drilling any of the wells to total depth.Improved operational efficiency.Cost savings in excess of US $500,000.00 It should be noted that these wells in this area typically cost between 2.5 and 3 million dollars to drill and complete. The 17–1/2" hole section is typically around 1200 ft with an associated cost of around US$800,000.00 over a period of six to seven days. The rig cost per day is of the order of US$50,000.00 Well A1 This well was drilled to a total depth of 5973 ft measured depth (5510ft TVD). Total drilling time was fifteen days at a cost of US $1,079,000.00.
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThis paper seeks to identify the causes and relative magnitudes of wellbore stability problems in a recently discovered, highly faulted field in Trinidad and Tobago. The two main factors that have been identified are reactive shales and tectonically stressed formations, which result in wellbore caving and seepage losses of mud under static conditions. Our data set includes every well drilled in the field to date. In order to determine whether problems are wholly formation related or are in part caused by drilling parameters, the following were analysed: 1.Rate of penetration per day in the formation of interest. This data was used to determine if wellbore cleaning problems were associated with high rates of penetration. Models for wellbore cleaning employed ranged from the simplistic CCI model to the more advanced service company methods. Parameters such as pump rates were inherently a part of this assessment. 2.Caliper logs to assess the degree of washouts in formations of interest. 3.Mudlogging data to identify the degree to which formation problems are tectonic or chemical in origin. 4.Comparison of mud type used in all wells to drill formations of interest in order to determine its relevance to the problem. 5.Assessment of bit type used in an effort to find out whether there was a higher low gravity solids (LGS) content in the mud with one or other bit type. This influences the hole cleaning properties of mud such as PV and YP. This paper documents a potential solution to the problems identified and details the drilling history of an exploratory well in a field where these conditions apply.It is hoped that the results of analysis presented in this paper will provide guidance for future exploration and appraisal programmes on the east coast of Trinidad.
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