Africa (Sub-Sahara) Marathon Oil has produced first gas from its Alba B3 compression platform offshore Equatorial Guinea. The startup enables the company to convert approximately 130 million BOE of proved undeveloped reserves, which more than doubles its remaining proved developed reserve base in the country. Marathon holds an operating interest of about 65% in the field, with Noble Energy holding the remaining stake. Aminex said that gas production from the Kiliwani North-1 well in Tanzania has reached 30 MMcf/D (about 5,000 BOE/D). The project's commissioning process is expected to conclude with a well test to determine the optimal production rate, which previous test data suggest will be approximately 30 MMcf/D, the company said. The operator of the Kiliwani North Development License, Aminex holds a 54.575% interest in the well.
The economic success of shale gas plays depends expansively on the brittle-ductile behavior of shale rock. The key parameter that separates the unconventional resources from conventional resources is the formation permeability, so all shale reservoirs need to be hydraulically fractured. Successful hydraulic fracturing requires targeting the most brittle rocks, therefore it is worthwhile to classify the shale in terms of brittle, less brittle, less ductile, and ductile zones. To identify the brittle-ductile transitional zone in shale reservoir, we have correlated the mineralogy-based brittleness index to elastic parameters estimated from well logs. The petrophysical model of the study area were plotted to break a story between brittle mineral contents, organic matter, brittleness indices and pore pressure to differentiate the brittle, ductile and transitional zones. Our results show that change in rock minerals distribution and brittleness index follow the trend in TOC, in less brittle to less ductile zone. In addition, we plotted the data in the crossplot of Young's modulus and Poisson's ratio and λρ-μρ lithology templates, noticed that shale with high quartz and high clay contents fall in less ductile to less brittle zone while shale with high quartz and low clay contents fall in less brittle to brittle zone. The overall observations of our study will support the previous research idea by suggesting the zone of brittle-ductile transition to design the hydraulic fracturing.
For a successful shale gas play in a region, the following characteristics (last but not least) need to be considered before going to the exploitation: (a) organic richness (TOC), (b) brittleness, (c) thickness, (d) gas-in-place, (e) permeability, (f) mineralogy, (g) maturation (Ro%) and (h) pore pressure (i) pore geometry (Zhu et al. 2011). Among these characteristics, shale brittleness is more critical to identify the desirable fracturing intervals and propagation for successful shale gas play (Wang and Gale, 2009). Van Dam et al. (2002) also documented in their research that brittleness is an important property that controls the failure process.
Widening supply and demand gap in natural gas industry, the advent of tight gas policy and increasing interest of operators in tight gas sands and shale has opened new venues for development of unconventional plays in Pakistan.
Middle Indus Basin hosts important gas fields of Pakistan. Most of the wells in this basin are completed in conventional lower Goru Sands. Lower Goru formation consists of inter-bedded sequences of sands and shale. Its unconventional sand and shale plays hold immense potential which has not yet been exploited due to lack of technology and promising economics. Moreover, Sembar shale is the well known source rock in this basin holding large shale gas potential. GIIP estimates for Lower Goru tight sands excluding the shale prospects are 8.4 TCF which are considered pessimistic due to lack of data in many fields.
From the currently suspended or abandoned wellbores of the Middle Indus Basin, a pilot project needs to be defined in each of the fields, to prove the technical and economical feasibility of tight Gas Potential of the Basin. Commencement of production from unconventional sands will enhance the production in a cost effective manner due to availability of infrastructure and facilities.
This paper focuses on the utilization of existing wellbores as well as data set and highlighting additional data acquisition requirements coupled with completion and multi-stage fracturing techniques for designing a pilot project. Case study of a pilot project in one of the fields of this basin is discussed. It encompasses the basic workflow, candidate selection criterion, Geo-mechanics, sector modeling, hydraulic fracture design and risk evaluation coupled with its use in full field development projects.
Background and Introduction
Pakistan's last year 2010-2011 production was about 3.91bcf/d, while its demand was (4.2bcf/d) and supply gap was also started. Since then the production from the conventional fields has decreased, while demand has been increased due to infrastructure and human needs. This huge shortfall in the gas market cannot be fulfilled with existing number of completions/producers. The conventional reserves of the country were 56 TCF out of which the country has already produced 50% of its conventional reserves. The recoverable remaining reserves are 24-28TCF, but will be produced at much lower production rate and in much longer period of time. The country has an infrastructure of Gas Processing Facilities 5bcf/d.
The explosive growth of shale gas production in the US has sparked a global race to determine which other regions from around the world have the potential to replicate this success. One of the main areas of focus is the Asia Pacific region, specifically Pakistan.
In this paper, real results from seven different US shale basins- Marcellus, Eagle Ford, Haynesville, Barnett, Woodford (West-Central Oklahoma), Fayetteville and Bakken- have been used to develop a comprehensive sequence of shale exploitation strategy for emerging shale plays. The study involves integration of shale gas exploitation knowledge reinforced by a decade of experience across most of the North American shale gas basins, with published data. Different reservoir properties have been compared to develop a comprehensive logic of the effective techniques to produce from shale-gas reservoirs. We have validated the sequence with real results from US shale production ventures, published case histories, and by global experts who have been directly involved in shale reserves evaluation and production.
Subsequently, several different reservoir attributes of Pakistan shale plays have been compared with US basins, in an attempt to identify analogues.
It is the intent of this paper to diminish the difficult and often expensive learning cycle time associated with a commercially successful shale project, as well as to attempt to illustrate the most influential factors that determine optimum production. A very few papers in the petroleum literature that provide an extensive and systematic approach towards shale exploitation strategy for given shale-reservoir conditions
Encouraged by the U.S. successful experience with shale plays, many Asia Pacific countries including China and India - having 1275 & 63 TCF of technically recoverable Shale gas respectively - have already started off with aggressive plans to exploit their vast shale reserves.
Pakistan is currently suffering an energy shortfall of 2.3 BCF and the energy demand is expected to increase further by 245% until 2022, as compared to 2008. As its conventional reserves deplete, there is a need to work on new frontiers of energy sources. Unconventional gas resources, such as shale gas, tight gas and coal bed methane, are the avenues that should be focused on, in the current scenario.
According to EIA estimates, Pakistan's total Risked Gas in Place is 206 TCF, while its Technically Producible Shale Reserves are 51 TCF. It is interesting to compare these postulations with the Sui gas field serving the energy needs of Pakistan for decades, and having an estimated original recoverable reserve of 12 TCF. However, efforts to develop this potential resource have been lacking perhaps due to the economic and technological challenges.