Africa (Sub-Sahara) Vaalco Energy started oil production from the Etame 12-H development well offshore Gabon. The well was drilled to a measured depth of approximately 3450 m and was targeting the recently discovered lower lobe of the Gamba reservoir. It was brought on line at a rate of 2,000 BOPD with no indication of hydrogen sulfide. Vaalco (28.07%) is the operator with partners Addax Petroleum (31.63%), Sasol (27.75%), Asia Pacific KrisEnergy started drilling the Rossukon-2 exploration well on Block G6/48 in the Gulf of Thailand, using the Key Gibraltar jackup rig. The well will reach a total depth at 5,462 ft and will test Early Miocene stacked fluvial sandstones on a broad structural high. The well will also appraise the Rossukon-1 reservoir, which produced 850 BOPD during tests.
Africa (Sub-Sahara) Bowleven began drilling operations at its Zingana exploration well on the Bomono permit in Cameroon. Located 20 km northwest of Douala, Cameroon's largest city, the well will target a Paleocene (Tertiary) aged, three-way dip closed fault block. The company plans to drill the well to a depth of 2000 m and will then spud a second well in Moambe, 2 km east of Zingana. Bowleven is the operator and holds 100% interest in the license. Asia Pacific China National Offshore Oil Company (CNOOC) has brought its Dongfang 1-1 gas field Phase I adjustment project on line ahead of schedule. The field is located in the Yinggehai basin of the Beibu Gulf in the South China Sea and has an average water depth of 70 m. The field is currently producing 53 MMcf/D of gas and is expected to reach its peak production of 54 MMcf/D before the end of the year.
Africa (Sub-Sahara) Bowleven has started drilling operations at the Moambe exploration well on the Bomono permit in Cameroon. Moambe is the second well in a two-well program, approximately 2 km east of the first well, Zingana. It targets a previously undrilled Paleocene Tertiary three-way dip fault block containing multiple sands and will be drilled to an estimated 1620 m in measured depth. Both wells will be logged. Bowleven is the operator and holds 100% interest. Asia Pacific Murphy Oil discovered gas at its Permai exploration well in deepwater Block H in the South China Sea offshore Malaysia. The find is Murphy's eighth consecutive success in the area around the Rotan floating liquefied natural gas project, which is planned to begin its first production in 2018.
Africa (Sub-Sahara) Sound Energy identified significant gas shows at the first Tendrara well onshore Morocco. Drilled to a 2665-m measured vertical depth, the well hit a total gross pay interval of 89 m of gas. The full set of well logs are being processed before the startup of rigless mechanical reservoir stimulation operations, which will be followed by a well test. The company is the operator of the well with a 55% working interest.
Africa (Sub-Sahara) Shell has initiated a two-well drilling program in blocks 1 and 4 of the Mafia Deep basin offshore Tanzania. Drilling is taking place in water depths of up to 7,545 ft, with the company and its joint-venture partners Pavilion Energy and Ophir Energy investing almost USD 80 million in the program. The two wells will meet the remaining requirements in the exploration licenses issued by the Tanzanian Ministry of Energy and Minerals. Asia Pacific Petronas has begun gas production from the world's first floating liquefied natural gas (FLNG) facility, the PFLNG SATU, at the Kanowit field offshore Malaysia's Sarawak state. The first-gas milestone marked the onset of commissioning and startup for the FLNG facility, preceding commercial production and initial cargo shipment. The facility is fitted with an external turret for operating in water depths of 229 ft to 656 ft. It will extract gas through a flexible subsea pipeline for the liquefaction, production, storage, and offloading of LNG at the field.
Enhanced Oil Recovery (EOR) has been utilized in Trinidad and Tobago for over 50 years. Most projects so far have focused on thermal as well as gas injection along with the more conventional waterfloods. In spite of that, recovery factors are still relatively low and the country's oil production has been declining for some time. Surprisingly, given the progress in chemical EOR and in particular polymer flooding in the last 10 years, these processes have not been used in Trinidad and we suggest that it might be time to consider their application. Similarly, foam has been used extensively worldwide to improve performances of gas and steam injection but has not yet been used in the country.
The situation of EOR in Trinidad will be first reviewed along with the characteristics of the main reservoirs. Then the potential for the application of chemical-based EOR methods such as polymer, surfactant and foams will be studied by comparing the characteristics of Trinidad's reservoirs to others worldwide which have seen the applications of chemical-based EOR methods.
This review and screening suggests that there is no technical barrier to the application of all these EOR methods in Trinidad. Most reservoirs produce heavy oil and are heavily faulted, but polymer injection has been widely applied in heavy oil reservoirs as well as in faulted reservoirs before, and suitable examples will be provided in the paper. Similarly, these characteristics do not present any specific difficulty for foam-enhanced gas or steam injection. The main issue appears to be the identification of suitable water sources for the projects.
This paper proposes a new look at EOR opportunities in Trinidad using conventional methods which have not been used in the country. This will help reservoir engineers who are considering such applications in the country and hopefully will eventually result in an increase in the oil production in the future.
Royalty Lease Evaluation (RLE) distillation analysis was performed on six hundred (600) wells in Petrotrin's Soldado acreage. This data has been traditionally generated for use by Petrotrin's refinery to determine if the crude oil feedstock is compatible to the refinery configuration or if the crude oil could cause yield, quality and production problems. These made for refinery reports have become part of Petrotrin's legacy data. The authors decided to examine this dormant dataset to ascertain what hidden stories it may tell about the oilfields from which they came.
In this investigation no data is generated, but an existing and dormant dataset will be analysed. Several components in a RLE distillation report on crude oil samples will be observed for trends, patterns and relationships. Ternary diagrams and cross-plots will be employed. Specific geochemical revelations from the RLE data will be validated by comparison to conventional gas chromatography data.
This investigation will illustrate how evaporative fractionation, which is a later charge of light hydrocarbons mixing with an emplaced biodegraded oil is evidenced by a phenomenon called the" Gas Oil Anomaly", seen in the RLE data. Essentially this is the absence of any gas oil fraction combined with the presence of light hydrocarbons in the distillation data. It will also be demonstrated that presence of the later charge of light hydrocarbons has been the key factor in the prolific production from the Soldado reservoirs.
Additional analysis of the light oil and gas oil fractions of a crude oil will reveal properties and characteristics that suggest there were different sources for both the originally emplaced oils and the later charge of light hydrocarbons. The data also shows that due to the evaporative fractionation phenomenon there is no correlation with API Gravity, oil viscosity, Sulphur content and depth of the reservoirs in Soldado. It will also be demonstrated that the data can be used as a qualitative tool leading to exploration plays in the Soldado acreage.
Explorationists at Petrotrin will find the results of this investigation to be both useful and provocative as it directs their attention to specific Trinmar Soldado oilfields as deep exploration play areas in a manner that traditional geochemical analyses have not been able to. It also allows the practioners in the Petrotrin Soldado acreage to better understand the productivity and complex fluid distributions in the Soldado reservoirs.
The issues and challenges encountered in exploiting cased hole reserves in mature oilfields on land in Trinidad, operated by Petrotrin, are presented, with mechanisms for overcoming these challenges.
Idle and uneconomic, low producing wells are identified as potential candidates and a documented workflow is followed. This opportunity is pursued on an annual basis via an NRT (New Reserve Type) project by the Petroleum Engineering Department. Conformance with the workflow provides a mechanism for risk mitigation. The petrophysical data set available for evaluating a prospective NRT is inadequate, electric logs are very old or not available. Production from the reservoir has changed the profile of the fluid content over the years and an electric log run in the past does not give a true reflection of the current fluid saturations. This leads to failed NRT’s. Net Oil sand maps in the past also do not reflect the current situation. It was also observed that poor cementation practices have given rise to situations where oil and water sands are poorly isolated.
Conforming to the documented procedures has minimized the risks and has resulted in successful NRT programs. The financial year 2014 – 2015 proved to be one of success for this project with an increase in oil production by 463 barrels of oil per day. Forty (40) recompletions were planned, to give an increase in production of 397 barrels of oil per day. Thirty eight (38) wells were attempted, of which thirty (30) wells were successfully recompleted and put on production.
The recent 3D seismic on land has provided a re-evaluation of reservoirs and structures and this is now being used as an input in improving the success rate. The learnings from this project play a significant role in informing the Company’s future business plans both in terms of upstream and downstream side of the business.
Since there are also a number of small operators, it is the intention to share our learnings so that these operators can cost effectively address the issues when encountered.
Plunger lift is a well-known artificial lift technique originally developed for the de-liquefaction of gas wells. However its use has been extended to include high Gas – Oil Ratio (GOR) oil wells, those with low or no production due to paraffin and scale deposits and wells with high or fluctuating sales line pressures. It is an intermittent production technique that utilizes reservoir energy stored in the gas phase to lift oil from the bottom of the well to surface via the vertical cyclic action of a "pigging" device within the tubing. This action enhances the production performance of liquid loaded wells.
In this study, plunger lift systems on two wells were evaluated to determine well performance and to optimize production rates if plunger lift systems were to be installed on other wells. Casing and tubing pressure trends were used to identify operational deficiencies and causes. Vogel's model was used to model the inflow performance relationship using bottom-hole pressure data. The Foss and Gaul model for plunger lift operation was used to determine production rates and gas requirement for each well in order to optimize well performance. The mode of operation with the current settings (long after-flow periods and over-estimation of plunger fall back time) is representative of intermittent lift with the assistance of a plunger rather than gas assisted plunger lift operation. The GOR for both wells are too low for efficient operation and a model of the current settings indicates that a gas injection rate of 450 MSCF/D is required to obtain an optimum oil production rate of 103 bopd. These plunger lift systems also prevent paraffin accumulations in the production tubing of these two wells.
New plunger lift operating variables such as casing valve opening and closing time, gas injection rate, after flow time, plunger rise velocity and fallback time, flow-line motor valve cycle time and number of cycles per day were modeled to obtain an optimum oil production rate. The results showed that a gas injection rate of 173 MSCF/D is required to obtain an oil production rate of 195 BOPD for a plunger rise velocity between 800 to 1000 ft/min. For these new settings the gas requirement was reduced by 61 % and the oil production increased by 89 %. These results indicate that the modification of the operating variables can effectively optimize gas assisted plunger lift systems that are installed in the oil wells producing from the Cruse Formation in the Main Soldado field offshore the Southwest coast of Trinidad.
Slim-hole drilling refers to the drilling of a well with a wellbore typically less than seven inches in diameter. Slim-hole drilling is beneficial to the low budget operator as there are considerable savings on rig time and costs and the rig size is ideal for drilling in remote areas. During slim-hole drilling, drilling fluid hydraulics is of great concern since significant pressure losses can occur in the drill pipe and annulus due to the reduced annular clearances. In addition, the flow regime generated in a slim-hole and the compatibility of the drilling fluid with the formation, can have an impact on the stability of the wellbore.
Slim-hole drilling has been successfully conducted onshore Trinidad in the Morne Diablo / Quinam Block for a number of years. The most commonly used drilling fluid is salt water based mud since it is cheaper and easier to dispose of than oil based mud. However the open literature did not show any studies conducted to determine the impact of drilling fluid hydraulics and drilling fluid compatibility on well-bore stability. In this study, twenty-five water based drilling mud formulations were prepared using different concentrations of sodium chloride, potassium chloride and calcium chloride. The rheological properties of each formulation were determined and the Bingham Plastic and Power Law models were applied. The frictional pressure losses for three commonly drilled slim-hole configurations were then computed and compared. Outcrop shale samples from the area were then treated with each formulation and the percentage loss in mass due to hydration and disintegration was measured for each sample.
The results from these two tests showed that of the mud formulations tested, overall, those with KCl (2.9 %) and CaCl2 (0.7 %), KCl (3.6 %), KCl (0.7 %) and NaCl (2.9 %), NaCl (0.7 %), and CaCl2 (2.9 %) were determined as best suitable for slim-hole drilling for the well configurations used. For these mud formulations, frictional pressure losses using both rheological models were the lowest and provide adequate rheological properties. The outcrop samples also showed the lowest percentage loss by mass when treated with these formulations indicating that they possess the desired wellbore inhibition properties. However, formulations containing NaCl only are the least expensive with straight KCl formulations being the most expensive.