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Farooqui, M.Y. (Gujarat State Petroleum Corp.) | Ghosh, Ujjal (Gujarat State Petroleum Corp.) | Ray, Arijit (GSPC) | Gupta, Sourabh Datta (Gujarat State Petroleum Corp) | Sarkar, Debjani (Gujarat State Petroleum Corp) | Ghosh, Priyam (Schlumberger) | Srigiriraju, Ramachandra (Schlumberger) | Sagar, Rajiv (Schlumberger) | Srivastva, Chandramani (Schlumberger) | Bhadra, Sutapa (Schlumberger) | Natarajan, Karthik Kumar (Schlumberger) | Agarwal, Gunja (Schlumberger) | Rao, Dhiresh Govind (Schlumberger) | Carrillat, Alexis
As the exploration for hydrocarbon resources continues to move into nontraditional areas, geologists are targeting reservoir rocks not usually associated with typical sedimentary-basin settings. One such group of rocks are volcanic rocks. In drilling 10 wells in the Deccan volcanic province in the Ingoli field in the Cambay basin, all wells encountered thick sections of Deccan basalt with intermittent fine-grained intratrappeans. However, only three of the wells produced hydrocarbon.
In this formation, conventional resistivity was unable to distinguish fluid saturations, so defining the hydrocarbon-bearing zones was not possible. A nonconventional and integrated approach successfully characterized the formation and the reservoir.
Using image logs, together with mud logs, we defined the facies that could be productive in this basalt formation.
All the geological information was used in material balance analysis to estimate possible ranges of original oil in place (OOIP). Well data, particularly borehole images, seismic attribute interpretation, geomechanical analysis, and reservoir and production data were used to understand the reservoir system, characterize the facies, and provide guidelines to delineate the reservoir. Significant uncertainties had to be addressed to ensure successful exploitation of significant remaining oil in place.
A number of multibean productivity tests and pressure buildup tests were acquired. Pressure transient analysis of these well test data, when incorporated with borehole image interpretation, provided important insights in understanding the productive reservoir facies. A conceptual geological model for the Ingoli basement reservoir is developed by integrating all the boreholederived geological information with seismic and reservoir analysis. The conceptual geological model forms a basis to consider the next steps of effectively exploiting the Ingoli field.
Alimuddin, Sultan (Pandit Deendayal Petroleum University) | Kumar, Neeraj (Pandit Deendayal Petroleum University) | Gandhi, Kanan (Pandit Deendayal Petroleum University) | Satyam, Swapnil (Pandit Deendayal Petroleum University)
To maximize oil and gas production profitability, it is paramount to reach the whole reservoir and extract the hydrocarbon resources efficiently. In offshore environments well prospects are sited at fracture gradients and narrow pressure gradients. Thus in this type of environment drilling hazards are aplenty and this makes wellbore completion a tough challenge. If the wellbore is not completed properly then there can be an economic as well as environmental disaster. In such situations there often exists a drilling window between fracture pressure gradient and also pore pressure through which when drilling done yields out proper results. Thus this paper overviews the possibility of applying MPD technique in Well construction and completion in offshore conditions.
The experimental as well as onsite usage of MPD technique has proved so far that this technique performs quicker and better than the conventional drilling technique which drills without any wellbore pressure management. Also the environmental hazards and risks related to conventional drilling usage in offshore hostile conditions are lowered through MPD. MPD can also reduce NPT as well as reduce drilling fluid loss which can in return lower the OPEX. MPD can also add value to production casings cementing operations in HPHT wells and also mitigate any further damage to wellbore.
Here in this paper MPD techniques and its case studies of usage on various offshore fields of India are reviewed and then the unique challenges associated with application of MPD in offshore basins of India are highlighted. Also here a proper drilling program using MPD has been proposed for various petroliferous basins of India. Albeit few offshore basins of India which have established proven reserves, many are still loosely explored and thus with the information available a new proposal using MPD has been conceived here for basins which are petroliferous for further drilling activity in the proposed basin. This in return will add knowledge to the stakeholders, government and operators for future planning and development of field. An effective comparison between conventional and MPD technique has also been highlighted in this paper for regulators of hydrocarbon industry for basic understanding of MPD.
Keywords: Managed Pressure Drilling, Fracture Pressure, Pore Pressure, Indian Offshore basins
Managed pressure drilling
With ever increasing population and waves of development in third world countries, the hunger for energy has also increased dramatically in the past few decades. In the beginning of 20th century oil supplied only 4% of energy demands and by the first decade of 21st century it supplies almost 40% of world energy and 96% of transportation energy . With such a increase in consumption rate of hydrocarbon so has the madness for recovering it which has made scientist and engineers to foray exploration and drilling activities in deep water and many other hostile environments of world. With easy prospects found post world war-2 being drilled in and consumed also, drilling in new discoveries nowadays which is mainly in harsher conditions is putting a lot of pressure on operators as drilling should be safe as well as cost-effective due to soaring high prices of crude oil. Considering all this scenarios Managed pressure drilling can be treated as an effective technology that may be cost effective by removing almost all the non productive time and also enabling drilling in prospects mainly in offshore conditions which are undrillable with conventional techniques.
Spurred by the commercial success of coalbed methane activity in USA, India initiated evaluating its coal bearing basins for their coalbed methane potential in 1992. In a short span of five years it tested and flowed coalbed methane from one of the coal seams of Barakar Formation in Jharia basin. This basin is one of the member basins of the Damodar-Koel coal belt of Eastern India. The basin cover an area of 450 square kilometers and exposes sediments of the Permian, Lower Gondwana Group. It is a half graben with the southern boundary fault being more pronounced than the northern boundary fault. The tectonic setting, physio-chemical, and reservoir characteristics, depth and thickness of coal seams, and production testing of one of the coal seams has resulted in demarcating the southern part of the basin to have an attractive coalbed methane play.
The central portion of this part of the basin has been prioritised for converting about 15 billion cubic meters of coalbed methane resources to reserves. Additional 15 billion cubic meters of methane resources could be converted to reserves from the adjoining areas.
Production of unconventional gas from sources like coal, shales and tight reservoirs is becoming increasingly important. In U.S.A. alone, this gas accounts for 20% of the production. Coalbed methane out numbers the other sources of gas by about 65%. Spurred by the U.S. success, many coal rich countries have launched exploration and production programmes to harness this resource. India, in 1992 embarked on evaluating its coal bearing basins for their coalbed methane potential. In 1997 India tested and flowed coalbed methane for the first time from a well drilled in the Parbatpur block of Jharia basin. Since then, concerted efforts are being made to cost effectively exploit this energy source. The Government of India has announced lucrative terms and conditions to attract investments in CBM exploration and production activities (Kelafant and Stern1).
India, which has the 6th largest coal reserves in the world, is expected to have potential for coalbed methane. About 99% of the coal reserves of India are found in the Gondwana basins while 1% lies within the Tertiary basins (Fig.-1). Some of the Gondwana basins have been prioritised for evaluating their coalbed methane plays. The prioritisation has been done on the basis of parameters suggested by Mandal and Ghosh2, wherein thirteen criterion are ranked from 1-10 with the least numeral having highest priority (Table-1). The priority that has emerged is as follows:
I. Jharia basin
II. East Bokaro basin
III. Raniganj basin
IV. North Karanpura basin
V. South Karanpura basin
VI. Rajmahal basin
VII. Pench-KanhanValley (Satpura Basin)
VIII. Pranhita-Godavari basin
The above prioritisation shows that the Rajmahal and Satpura basins are of the same rank. Priority has been given to the former because it has thicker coal seams.
Since coalbed methane exploration and exploitation activity in India is still in the initial stages these activities are in the R & D phase. Concerted efforts integrating geo-scientific, reservoir and production characteristics to evaluate the coalbed methane play of Jharia basin are discussed in this paper.