Dean Oliver

SPEJ has long been recognized as the premier journal for petroleum engineering research. That opinion is reinforced by its ranking in impact factor. Impact factor is a measure of the influence that a journal has on the research discipline. Impact factor does not compare well across disciplines, but within a discipline, it can be a useful measure of a publication’s importance. The impact factor for 2006 is calculated by dividing the number of citations to SPEJ papers from 2004 and 2005 by the total number of SPEJ articles published in 2004 and 2005. An impact factor of 1.0 means that, on average, the articles published 1 or 2 years ago have been cited one time. This impact factor does not count citations in SPE conference proceedings.

In 2004 and 2005, there were a total of 88 articles published in SPEJ. In 2006, there were 71 citations to those articles. The impact factor for SPEJ in 2006 is therefore 71/88 = 0.806. This is 30% higher than the impact factor for the second-ranked petroleum engineering journal.

Impact factor only tells a part of the story. It is interesting, for example, to see who cites SPEJ papers. Some of my colleagues and I have tended to believe that SPEJ papers are primarily cited by other SPEJ papers or by other SPE technical journals. However, Table 1 tells a different story. For the year 2006, it summarizes the source of all citations to SPEJ articles. Thus, in 2006, there were 1,034 citations of SPEJ articles. Of those citations, only 94 (less than 10%) were in SPEJ itself. The other 90% are citations by papers from other petroleum engineering, groundwater, chemical engineering, and numerical analysis journals. Some indication of the breadth of SPEJ’s impact can be ascertained by the fact that citations from the top 11 journals only account for 52% of all citations for the year.

Although it can easily be argued that all citations to journal articles are important, only citations of 2004 and 2005 articles are used to compute impact factor. I have plotted the data in Fig. 1 in a way that emphasizes key features of the citation patterns that affect impact factor. Note first that papers that are only 1 year old are cited somewhat infrequently, and that the most frequently cited papers are those that are 2 to 4 years old. Citations of older articles gradually decrease with time. This is common to petroleum engineering journals in general. Note also that, although citations of SPEJ papers to other SPEJ papers account for only 10% of the total, they account for over 40% of citations to articles published in the current and preceding year. We can speculate that the higher percentage of SPEJ self-citations in the most recent years (compared to other journals) is the result of the care we take in correctly accounting for the conversion of SPE conference proceedings to SPEJ articles.

Data to address questions of that sort can only be gathered from the papers themselves. Out of curiosity, I scanned the reference lists from nine of the papers in one recent issue of SPEJ. The manuscripts contained a total of 203 references (23 per article). Sixty-eight of the references were to SPE conference proceedings, and only 10 were to SPEJ articles. While this may indicate that it is not a representative sample, the interesting thing is that at least five of the conference papers that were referenced should have been references to SPEJ papers—not to the original conference proceedings they replaced. This is something to which authors and editors should pay close attention.

The Review Chairs and editors will gather again at the SPE Annual Technical Conference and Exhibition in Anaheim, California, 11–14 November, to discuss ways to improve the journal and the review process. It is good to know, however, that the SPE Journal remains strong in many ways, including an influence that stretches far beyond the traditional petroleum engineering community. The impact factor is the highest in petroleum engineering, but could be higher if the time for publication were to be reduced and if more care were taken to ensure that citations are to journal articles, and not to the conference proceedings from which they were derived.

Thanks for your continued participation and support; I hope you enjoy the September issue.